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Sample records for ac electric field

  1. Dynamics of a nanowire superlattice in an ac electric field

    Zhang, Aizhen; Voon, L. C. Lew Yan; M. Willatzen

    2005-01-01

    With a one-band envelope function theory, we investigate the dynamics of a finite nanowire superlattice driven by an ac electric field by solving numerically the time-dependent Schroedinger equation. We find that for an ac electric field resonant with two energy levels located in two different minibands, the coherent dynamics in nanowire superlattices is much more complex as compared to the standard two-level description. Depending on the energy levels involved in the transitions, the coheren...

  2. Aligned Immobilization of Proteins Using AC Electric Fields.

    Laux, Eva-Maria; Knigge, Xenia; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

    2016-03-01

    Protein molecules are aligned and immobilized from solution by AC electric fields. In a single-step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X-ray crystal data. PMID:26779699

  3. Magnetophoresis of neutral particles in AC electric field

    Ovchinnikov, A. A.

    2002-01-01

    It has been shown that under joint action of DC magnetic and AC electric fields neutral particles (atoms,molecules,nano-size particles etc.) nearby interface move with permanent velocity along the surface. The driving force depends on non-linear dynamical properties of polarization of the particles and a coupling between the polarisation and the position of the particles on a surface.

  4. Effects of AC Electric Field on Small Laminar Nonpremixed Flames

    Xiong, Yuan

    2015-04-01

    Electric field can be a viable method in controlling various combustion properties. Comparing to traditional actuators, an application of electric field requires very small power consumption. Especially, alternating current (AC) has received attention recently, since it could modulate flames appreciably even for the cases when direct current (DC) has minimal effects. In this study, the effect of AC electric fields on small coflow diffusion flames is focused with applications of various laser diagnostic techniques. Flow characteristics of baseline diffusion flames, which corresponds to stationary small coflow diffusion flames when electric field is not applied, were firstly investigated with a particular focus on the flow field in near-nozzle region with the buoyancy force exerted on fuels due to density differences among fuel, ambient air, and burnt gas. The result showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle exit. Nozzle heating effect influenced this near-nozzle flow-field particularly among lighter fuels. Numerical simulations were also conducted and the results showed that a fuel inlet boundary condition with a fully developed velocity profile for cases with long fuel tubes should be specified inside the fuel tube to obtain satisfactory agreement in both the flow and temperature fields with those from experiment. With sub-critical AC applied to the baseline flames, particle image velocimetry (PIV), light scattering, laser-induced incandescence (LII), and laser-induced fluores- cence (LIF) techniques were adopted to identify the flow field and the structures of OH, polycyclic aromatic hydrocarbons (PAHs), soot zone. Under certain AC condi- tions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered from the

  5. Elastic constant of Dendrobium protoplasts in AC electric fields

    Pikul Wanichapichart

    2002-11-01

    Full Text Available This work reports elongation of Dendrobium protoplasts in an ac electric field between two cylindrical electrodes. A protoplast firstly was translated towards an electrode by dielectrophoretic force in 17 kV.m-1 field strength at 1 MHz, and secondly it was elongated due to an interaction between an induced electric dipole (μ and the electric field (E. Protoplast elongation was observed by varying both the field strength at 30, 45, 60, and 85 kV.m-1 and field frequency at 0.5, 1, 5, and 10 MHz. For a given field frequency and field strength, a parameter a/b (major/minor axis was measured as the protoplast elongation.Two-step elongation and restoration phases were observed. The former was completed within 2 minutes of field exposure, and the latter was completed within 15 seconds regardless of the field exposure time between 3 and 20 minutes. The evidence of a complete restoration indicated that the elasticity of the protoplast membrane obeyed Hooke’s law. This study also found that elastic constant k of the membrane varied non-linearly with the field strength. It was found to be from 0.04 to 0.08 mN.m-1, dependent on the field frequency.

  6. AC Electric Field Activated Shape Memory Polymer Composite

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  7. Effect of AC electric fields on flame spread over electrical wire

    Kim, Minkuk

    2011-01-01

    The effect of electric fields on the characteristics of flame spread over insulated electrical wire has been investigated experimentally by varying AC voltage and frequency applied to the wire in the normal gravity condition. The polyethylene (PE) insulated electrical wire was placed horizontally on electrically non-conducting posts and one end of the wire was connected to the high voltage terminal. Thus, the electrical system is the single electrode configuration. The wire was ignited at one end and the flame spread rate along the wire has been measured from the images using a video camera. Two distinct regimes existed depending on the applied AC frequency. In the low frequency regime, the flame spread rate decreased with the frequency and voltage. While in the high frequency regime, it decreased initially with voltage and then increased. At high frequency, the spread rate was even over that without applying electric fields. This result implies that fire safety codes developed without considering the effect of electric fields may require modifications. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  8. AC electric field induced vortex in laminar coflow diffusion flames

    Xiong, Yuan

    2014-09-22

    Experiments were performed by applying sub-critical high-voltage alternating current (AC) to the nozzle of laminar propane coflow diffusion flames. Light scattering, laser-induced incandescence and laser-induced fluorescence techniques were used to identify the soot zone, and the structures of OH and polycyclic aromatic hydrocarbons (PAHs). Particle image velocimetry was adopted to quantify the velocity field. Under certain AC conditions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. The onset conditions for the vortex formation supported the role of an electromagnetic force acting on charged particles in the flame zone. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  9. Effect of AC electric fields on the stabilization of premixed bunsen flames

    Kim, Minkuk

    2011-01-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally for stoichiometric methane-air mixture by applying AC voltage to the nozzle with the single-electrode configuration. The detachment velocity either at blowoff or partial-detachment has been measured by varying the applied voltage and frequency of AC. The result showed that the detachment velocity increased with the applied AC electric fields, such that the flame could be nozzle-attached even over five times of the blowoff velocity without having electric fields. There existed four distinct regimes depending on applied AC voltage and frequency. In the low voltage regime, the threshold condition of AC electric fields was identified, below which the effect of electric fields on the detachment velocity is minimal. In the moderate voltage regime, the flame base oscillated with the frequency synchronized to AC frequency and the detachment velocity increased linearly with the applied AC voltage and nonlinearly with the frequency. In the high voltage regime, two different sub-regimes depending on AC frequency were observed. For relatively low frequency, the flame base oscillated with the applied AC frequency together with the half frequency and the variation of the detachment velocity was insensitive to the applied voltage. For relatively high frequency, the stabilization of the flame was significantly affected by the generation of streamers and the detachment velocity decreased with the applied voltage. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  10. C/NOFS Observations of AC Electric Field Fields Associated with Equatorial Spread-F

    Pfaff, R.; Liebrecht, C.

    2009-01-01

    The Vector Electric Field Investigation (VEFI) on the C/NOFS equatorial satellite provides a unique data set in which to acquire detailed knowledge of irregularities associated with the equatorial ionosphere and in particular with spread-F depletions. We present vector AC electric field observations, primarily gathered within the ELF band (1 Hz to 250 Hz) on C/NOFS that address a variety of key questions regarding how plasma irregularities, from meter to kilometer scales, are created and evolve. The data will be used to explore the anisotropy/isotropy of the waves, their wavelength and phase velocity, as well as their spectral distributions. When analyzed in conjunction with the driving DC electric fields and detailed plasma number density measurements, the combined data reveal important information concerning the instability mechanisms themselves. We also present high resolution, vector measurements of intense lower hybrid waves that have been detected on numerous occasions by the VEFI burst memory VLF electric field channels.

  11. AC Electric Fields Drive Steady Flows in Flames

    Drews, Aaron M.; Cademartiri, Ludovico; Chemama, Michael Leopold; Brenner, Michael P.; Whitesides, George M.; Bishop, Kyle J. M.

    2012-01-01

    We show that time-oscillating electric fields applied to plasmas present in flames create steady flows of gas. Ions generated within the flame move in the field and migrate a distance δ before recombining; the net flow of ions away from the flame creates a time-averaged force that drives the steady flows observed experimentally. A quantitative model describes the response of the flame and reveals how δ decreases as the frequency of the applied field increases. Interestingly, above a critical ...

  12. Electro-worming: The Behaviors of Caenorhabditis (C.) elegans in DC and AC Electric Fields

    Chuang, Han-Sheng; Dabbish, Nooreen; Bau, Haim

    2010-01-01

    The video showcases how C. elegans worms respond to DC and AC electrical stimulations. Gabel et al (2007) demonstrated that in the presence of DC and low frequency AC fields, worms of stage L2 and larger propel themselves towards the cathode. Rezai et al (2010) have demonstrated that this phenomenon, dubbed electrotaxis, can be used to control the motion of worms. In the video, we reproduce Rezai's experimental results. Furthermore, we show, for the first time, that worms can be trapped with high frequency, nonuniform electric fields. We studied the effect of the electric field on the nematode as a function of field intensity and frequency and identified a range of electric field intensities and frequencies that trap worms without apparent adverse effect on their viability. Worms tethered by dielectrophoresis (DEP) avoid blue light, indicating that at least some of the nervous system functions remain unimpaired in the presence of the electric field. DEP is useful to dynamically confine nematodes for observati...

  13. Dynamical polarizability of graphene irradiated by circularly polarized ac electric fields

    Busl, Maria; Platero, Gloria; Jauho, Antti-Pekka

    2012-01-01

    We examine the low-energy physics of graphene in the presence of a circularly polarized electric field in the terahertz regime. Specifically, we derive a general expression for the dynamical polarizability of graphene irradiated by an ac electric field. Several approximations are developed that...... allow one to develop a semianalytical theory for the weak-field regime. The ac field changes qualitatively the single- and many-electron excitations of graphene: Undoped samples may exhibit collective excitations (in contrast to the equilibrium situation), and the properties of the excitations in doped...... graphene are strongly influenced by the ac field. We also show that the intensity of the external field is the critical control parameter for the stability of these excitations....

  14. Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge

    Goldberg, Benjamin M.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-08-01

    The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly ‘flat top’ distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present

  15. Experimental Investigation of the Corona Discharge in Electrical Transmission due to AC/DC Electric Fields

    Fuangpian Phanupong

    2016-01-01

    Full Text Available Nowadays, using of High Voltage Direct Current (HVDC transmission to maximize the transmission efficiency, bulk power transmission, connection of renewable power source from wind farm to the grid is of prime concern for the utility. However, due to the high electric field stress from Direct Current (DC line, the corona discharge can easily be occurred at the conductor surface leading to transmission loss. Therefore, the polarity effect of DC lines on corona inception and breakdown voltage should be investigated. In this work, the effect of DC polarity and Alternating Current (AC field stress on corona inception voltage and corona discharge is investigated on various test objects, such as High Voltage (HV needle, needle at ground plane, internal defect, surface discharge, underground cable without cable termination, cable termination with simulated defect and bare overhead conductor. The corona discharge is measured by partial discharge measurement device with high-frequency current transformer. Finally, the relationship between supply voltage and discharge intensity on each DC polarity and AC field stress can be successfully determined.

  16. Electric field distribution and effective nonlinear AC and DC responses of graded cylindrical composites

    Ding Xia; Jia Yan-Xia; Wei En-Bo

    2012-01-01

    The perturbation method is used to study the localization of electric field distribution and the effective nonlinear response of graded composites under an external alternating-current(AC)and direct-current(DC)electric field Eapp=E0(1 + sin wt).The dielectric profile of the cylindrical inclusions is modeled by function ei(r)=Ckrκ(r ≤ a),where r is the radius of the cylindrical inclusion,and Cκ,k,a are parameters.In the dilute limit,the local potentials and the effective nonlinear responses at all harmonics are derived.Meanwhile,the general effective nonlinear responses are also derived and compared with the effective nonlinear responses at harmonics under the AC and DC external field.It is found that the effective nonlinear AC and DC responses at harmonics can be calculated by those of the general effective nonlinear of the graded composites under the external DC electric field.Moreover,the obtained local electrical fields show that the electrical field distribution in the cylindrical inclusions is controllable,and the maximum of the electric field inside the cylinder is at its center.

  17. Resonant tunneling of interacting electrons in an AC electric field

    The problem of the effect of electron-electron interaction on the static and dynamic properties of a double-barrier nanostructure (resonant tunneling diode (RTD)) is studied in terms of a coherent tunneling model, which includes a set of Schrödinger and Poisson equations with open boundary conditions. Explicit analytical expressions are derived for dc and ac potentials and reduced (active and reactive) currents in the quasi-classical approximation over a wide frequency range. These expressions are used to analyze the frequency characteristics of RTD. It is shown that the interaction can radically change the form of these expressions, especially in the case of a hysteretic I-V characteristic. In this case, the active current and the ac potentials can increase sharply at both low and high frequencies. For this increase to occur, it is necessary to meet quantum regime conditions and to choose a proper working point in the I-V characteristic of RTD. The possibility of appearance of specific plasma oscillations, which can improve the high-frequency characteristics of RTD, is predicted. It is found that the active current can be comparable with the resonant dc current of RTD

  18. Resonant tunneling of interacting electrons in an AC electric field

    Elesin, V. F., E-mail: VFElesin@mephi.ru [National Research Nuclear University MEPhI (Russian Federation)

    2013-11-15

    The problem of the effect of electron-electron interaction on the static and dynamic properties of a double-barrier nanostructure (resonant tunneling diode (RTD)) is studied in terms of a coherent tunneling model, which includes a set of Schrödinger and Poisson equations with open boundary conditions. Explicit analytical expressions are derived for dc and ac potentials and reduced (active and reactive) currents in the quasi-classical approximation over a wide frequency range. These expressions are used to analyze the frequency characteristics of RTD. It is shown that the interaction can radically change the form of these expressions, especially in the case of a hysteretic I-V characteristic. In this case, the active current and the ac potentials can increase sharply at both low and high frequencies. For this increase to occur, it is necessary to meet quantum regime conditions and to choose a proper working point in the I-V characteristic of RTD. The possibility of appearance of specific plasma oscillations, which can improve the high-frequency characteristics of RTD, is predicted. It is found that the active current can be comparable with the resonant dc current of RTD.

  19. Experimental study on the effects of AC electric fields on flame spreading over polyethylene-insulated electric-wire

    Jin, Young Kyu

    2010-11-01

    In this present study, we experimentally investigated the effects of electric fields on the characteristics of flames spreading over electric-wires with AC fields. The dependence of the rate at which a flame spreads over polyethylene-insulated wires on the frequency and amplitude of the applied AC electric field was examined. The spreading of the flame can be categorized into linear spreading and non-linearly accelerated spreading of flame. This categorization is based on the axial distribution of the field strength of the applied electric field. The rate at which the flame spreads is highly dependent on the inclined direction of the wire fire. It could be possible to explain the spreading of the flame on the basis of thermal balance. © 2010 The Korean Society of Mechanical Engineers.

  20. AC electric field induced droplet deformation in a microfluidic T-junction.

    Xi, Heng-Dong; Guo, Wei; Leniart, Michael; Chong, Zhuang Zhi; Tan, Say Hwa

    2016-08-01

    We present for the first time an experimental study on the droplet deformation induced by an AC electric field in droplet-based microfluidics. It is found that the deformation of the droplets becomes stronger with increasing electric field intensity and frequency. The measured electric field intensity dependence of the droplet deformation is consistent with an early theoretical prediction for stationary droplets. We also proposed a simple equivalent circuit model to account for the frequency dependence of the droplet deformation. The model well explains our experimental observations. In addition, we found that the droplets can be deformed repeatedly by applying an amplitude modulation (AM) signal. PMID:27173587

  1. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    Zhao, Guangpu [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Jian, Yongjun, E-mail: jianyj@imu.edu.cn [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Chang, Long [School of Mathematics and Statistics, Inner Mongolia University of Finance and Economics, Hohhot, Inner Mongolia 010051 (China); Buren, Mandula [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China)

    2015-08-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed.

  2. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed

  3. Effect of ac electric fields on counterflow diffusion flame of methane

    Chul Choi, Byung

    2012-08-01

    The effect of electric fields on the response of diffusion flames in a counterflow has been investigated experimentally by varying the AC voltage and frequency. The result showed that the flame was stationary with high AC frequency above the threshold frequency, and it increased with the applied voltage and then leveled off at 35 Hz. Below the threshold frequency, however, the flame oscillated with a frequency that was synchronized with the applied AC frequency. This oscillation can be attributed to the ionic wind effect due to the generation of bulk flow, which arises from the momentum transfer by molecular collisions between neutral molecules and ions, where the ions in the reaction zone were accelerated by the Lorentz force. © 2012 The Korean Society of Mechanical Engineers.

  4. Experimental Study on Downwardly Spreading Flame over Inclined Polyethylene-insulated Electrical Wire with Applied AC Electric Fields

    Lim, Seung Jae

    2014-12-30

    An experimental study on downwardly spreading flame over slanted electrical wire, which is insulated by Polyethylene (PE), was conducted with applied AC electric fields. The result showed that the flame spread rate decreased initially with increase in inclination angle of wire and then became nearly constant. The flame shape was modified significantly with applied AC electric field due to the effect of ionic wind. Such a variation in flame spread rate could be explained by a thermal balance mechanism, depending on flame shape and slanted direction of flame. Extinction of the spreading flame was not related to angle of inclination, and was described well by a functional dependency upon the frequency and voltage at extinction.

  5. Deformation and Interaction of Droplet Pairs in a Microchannel Under ac Electric Fields

    Chen, Xiaodong; Song, Yongxin; Li, Dongqing; Hu, Guoqing

    2015-08-01

    The deformation and interaction of a droplet pair in an electric field determine the success of droplet coalescence. Electric intensity and initial droplet separation are crucial parameters in this process. In this work, a combined theoretical and numerical analysis is performed to study the electrohydrodynamics of confined droplet pairs in a rectangular microchannel under ac electric fields. We develop a theoretical model to predict the relationship between critical electric intensity and droplet separation. A geometrical model relating the initial droplet separation to the cone angle is also established to determine the critical separation for partial coalescence. These models are validated by comparisons with existing experimental observations. According to the initial separation and electric intensity, five regimes of droplet interactions are classified by direct numerical simulations, namely noncoalescence, coalescence, partial coalescence, ejection after coalescence, and ejection with partial coalescence. According to their controlling mechanisms, the five regimes are distinguished by three well-defined boundaries. The detailed dynamics of the partial coalescence phenomenon is resolved when the droplet separation exceeds the critical value. A dynamic liquid bridge between the droplets is sustained by the competition between surface tension and electric stress. The dynamics of ejected microjets at the exterior ends are also addressed to show their responses to the oscillating electric field. The full understanding of the droplet dynamics under electric fields can be used to predict the droplet fusion behaviors and thus to facilitate the design of droplet-based microfluidic devices.

  6. Effective Response of Nonlinear Composite under External AC and DC Electric Field

    LIU Ye; LIANG Fang-Chu; SHEN Hong-Liang

    2005-01-01

    A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, Dα = εαE + xα|E|2E. Under the external AC and DC electric field Eapp = Eα(1 + sinwt), the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute limit.

  7. Dynamic characteristics and electromechanical fields of 1-3 piezoelectric/polymer composites under AC electric fields

    This paper studies the dynamic electromechanical response of 1-3 piezoelectric/polymer composites under alternating current (AC) electric fields. The piezocomposites contain square or circular piezoelectric rods in an epoxy matrix. Experiments were conducted to measure the electrical impedance and phase angle at various frequencies, using the device specimen of the 1-3 piezocomposites. Three dimensional finite element analysis was also employed to calculate the frequency characteristics, and a comparison is made between simulation and experiment. The dynamic electromechanical fields in the 1-3 piezocomposites are then discussed in detail

  8. Effective response in nonlinear spherical coated composites under external AC and DC electric fields

    Bao Shu-Hong; Chen Xiao-Gang; Li Qian-Qian; Guo Jun-Ming; Zhai Li-Li

    2012-01-01

    By using the perturbation method,effective nonlinear direct current (DC) and alternating current (AC) responses of nonlinear composites with spherical coated inclusions randomly embedded in a host medium are studied under the action of an external electric field Ea =E0 + E1 sin ωt + E3 sin 3ωt with different amplitudes and frequencies.The local potentials of composites at all harmonics are given in the inclusion particles and the host regions.All effective nonlinear responses to composites and the relationship between the effective nonlinear responses at all harmonics are also deduced for the spherical coated inclusions in a dilute limit.

  9. Accelerated Detection of Viral Particles by Combining AC Electric Field Effects and Micro-Raman Spectroscopy

    Matthew Robert Tomkins

    2015-01-01

    Full Text Available A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the “fingerprinting” capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres captured by an AC electric field between planar microelectrodes is presented with a methodology for analyzing the resulting spectra by comparing relative peak intensities. The same principle is applied to dielectrophoretically captured M13 phage particles whose presence is indirectly confirmed with micro-Raman spectroscopy using NeutrAvidin-Cy3 as a labeling molecule. It is concluded that the combination of electrokinetically driven virus sampling and micro-Raman based signal transduction provides a promising approach for time-efficient and in situ detection of viruses.

  10. Keratinocyte galvanotaxis in combined DC and AC electric fields supports an electromechanical transduction sensing mechanism.

    Hart, Francis X; Laird, Mhairi; Riding, Aimie; Pullar, Christine E

    2013-02-01

    Sedentary keratinocytes at the edge of a skin wound migrate into the wound, guided by the generation of an endogenous electric field (EF) generated by the collapse of the transepithelial potential. The center of the wound quickly becomes more negative than the surrounding tissue and remains the cathode of the endogenous EF until the wound is completely re-epithelialized. This endogenous guidance cue can be studied in vitro. When placed in a direct current (DC) EF of physiological strength, 100 V/m, keratinocytes migrate directionally toward the cathode in a process known as galvanotaxis. Although a number of membrane-bound (e.g., epidermal growth factor receptor (EGFR), integrins) and cytosolic proteins (cAMP, ERK, PI3K) are known to play a role in the downstream signaling mechanisms underpinning galvanotaxis, the initial sensing mechanism for this response is not understood. To investigate the EF sensor, we studied the migration of keratinocytes in a DC EF of 100 V/m, alternating current (AC) EFs of 40 V/m at either 1.6 or 160 Hz, and combinations of DC and AC EFs. In the AC EFs alone, keratinocytes migrated randomly. The 1.6 Hz AC EF combined with the DC EF suppressed the direction of migration but had no effect on speed. In contrast, the 160 Hz AC EF combined with the DC EF did not affect the direction of migration but increased the migration speed compared to the DC EF alone. These results can be understood in terms of an electromechanical transduction model, but not an electrodiffusion/osmosis or a voltage-gated channel model. PMID:22907479

  11. Experimental Investigation of the Corona Discharge in Electrical Transmission due to AC/DC Electric Fields

    Fuangpian Phanupong; Zafar Taimoor; Ruankorn Sayan; Suwanasri Thanapong

    2016-01-01

    Nowadays, using of High Voltage Direct Current (HVDC) transmission to maximize the transmission efficiency, bulk power transmission, connection of renewable power source from wind farm to the grid is of prime concern for the utility. However, due to the high electric field stress from Direct Current (DC) line, the corona discharge can easily be occurred at the conductor surface leading to transmission loss. Therefore, the polarity effect of DC lines on corona inception and breakdown voltage s...

  12. Human aquaporin 4 gating dynamics in dc and ac electric fields: A molecular dynamics study

    Garate, J.-A.; English, Niall J.; MacElroy, J. M. D.

    2011-02-01

    Water self-diffusion within human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of external ac and dc electric fields. The computed diffusive (pd) and osmotic (pf) permeabilities under zero-field conditions are (0.718 ± 0.24) × 10-14 cm3 s-1 and (2.94 ± 0.47) × 10-14 cm3 s-1, respectively; our pf agrees with the experimental value of (1.50 ± 0.6) × 10-14 cm3 s-1. A gating mechanism has been proposed in which side-chain dynamics of residue H201, located in the selectivity filter, play an essential role. In addition, for nonequilibrium MD in external fields, it was found that water dipole orientation within the constriction region of the channel is affected by electric fields (e-fields) and that this governs the permeability. It was also found that the rate of side-chain flipping motion of residue H201 is increased in the presence of e-fields, which influences water conductivity further.

  13. Frequency-dependent electrodeformation of giant phospholipid vesicles in AC electric field

    Peterlin, Primoz

    2010-01-01

    A model of vesicle electrodeformation is described which obtains a parametrized vesicle shape by minimizing the sum of the membrane bending energy and the energy due to the electric field. Both the vesicle membrane and the aqueous media inside and outside the vesicle are treated as leaky dielectrics, and the vesicle itself is modelled as a nearly spherical shape enclosed within a thin membrane. It is demonstrated (a) that the model achieves a good quantitative agreement with the experimentally determined prolate-to-oblate transition frequencies in the kHz range, and (b) that the model can explain a phase diagram of shapes of giant phospholipid vesicles with respect to two parameters: the frequency of the applied AC electric field and the ratio of the electrical conductivities of the aqueous media inside and outside the vesicle, explored in a recent paper (S. Aranda et al., Biophys. J. 95:L19--L21, 2008). A possible use of the frequency-dependent shape transitions of phospholipid vesicles in conductometry of m...

  14. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters.

  15. Influence of electric field DC-component on AC-response of ferroelectric powder

    F. Starzyk

    2008-01-01

    Full Text Available Purpose: of this work was to establish whether ac-response of freely stocked micro-granular ferroelectric matter on fringe measuring electric field depends on constant component presence VDC (or DC-Bias.Design/methodology/approach: used involves measurements of effective dielectric permittivity (and other effective dielectric quantities by means of interdigit dielectrometry. Fringe measuring electric field was applied to BaTiO3 micro-powder by interdigit comb sensor (ICS Netzsch of Ms25 type. ICS was driven by measuring generator with sinusoidal voltage: v(t= VDC+VACsin(ωt, within frequency range 20Hz-100kHz and for DC-Bias values ranging as VDC=(0-20V.Findings: The interdigit dielectrometry was applied to measure complex dielectric permittivity, complex dielectric modulus and others dielectric functions of ferroelectric BaTiO3 powder. The influence of constant component of electric stimulus was investigated in the frequency range 100 kHz to 20 Hz. It was established that in the low frequency range constant component of electric field enhances effective dielectric permittivity, and changes two weak relaxation processes occurring in the ferroelectric micro-granular net. It turned out that effective dielectric complex modulus of this net is most sensitive quantity for application of constant component of electric stimulus.Research limitations/implications: The density solution effect is a source of small effective dielectric permittivity of micro-granular ferroelectric powder (ε’. ε’ values are being enhanced by presence of non zero VDC value. The same effect was established for effective energy loss coefficient (ε”. The two relaxational processes connected with VDC≠0 seems to be a key feature of freely stocked ferroelectric matter.Originality/value: of this work relays on the fact, that this is a first report of the VDC influence on effective dielectric properties of ferroelectric micro-granular matter. It is opening the way to a new

  16. Growth of aligned single-walled carbon nanotubes under ac electric fields through floating catalyst chemical vapour deposition

    Dou Xin-Yuan; Luo Shu-Dong; Zhang Zeng-Xing; Liu Dong-Fang; Wang Jian-Xiong; Gao Yan; Zhou Wei-Ya; Wang Gang; Zhou Zhen-Ping; Tan Ping-Heng; Zhou Jian-Jun; Song Li; Sun Lian-Feng; Jiang Peng; Liu Li-Feng; Zhao Xiao-Wei

    2005-01-01

    Through floating catalyst chemical vapour deposition(CVD) method, well-aligned isolated single-walled carbon nanotubes (SWCNTs) and their bundles were deposited on the metal electrodes patterned on the SiO2/Si surface under ac electric fields at relatively low temperature(280℃). It was indicated that SWCNTs were effectively aligned under ac electric fields after they had just grown in the furnace. The time for a SWCNT to be aligned in the electric field and the effect of gas flow were estimated. Polarized Raman scattering was performed to characterize the aligned structure of SWCNTs. This method would be very useful for the controlled fabrication and preparation of SWCNTs in practical applications.

  17. Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress

    Liu, Z.; Liu, Q.; Wang, Z. D.

    2016-05-01

    This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid’s streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform.

  18. Self-sustained firing activities of the cortical network with plastic rules in weak AC electrical fields

    Both external and endogenous electrical fields widely exist in the environment of cortical neurons. The effects of a weak alternating current (AC) field on a neural network model with synaptic plasticity are studied. It is found that self-sustained rhythmic firing patterns, which are closely correlated with the cognitive functions, are significantly modified due to the self-organizing of the network in the weak AC field. The activities of the neural networks are affected by the synaptic connection strength, the external stimuli, and so on. In the presence of learning rules, the synaptic connections can be modulated by the external stimuli, which will further enhance the sensitivity of the network to the external signal. The properties of the external AC stimuli can serve as control parameters in modulating the evolution of the neural network. (interdisciplinary physics and related areas of science and technology)

  19. Effective Response of Nonlinear Spherical Coated Composites Under External AC and DC Electric Field

    SHEN Yu-Yan; CHEN Xiao-Gang; LI Qian-Qian; CUI Wei; HAO Yan-Hua

    2009-01-01

    Under the external A C and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displacement and electric field, is investigated in the dilute limit by using the perturbation method.The local potentials in inclusion and host regions are derived at all harmonics.Moreover, the formu/ae of the effective linear and nonlinear responses are given in the dilute limit.

  20. AC electric field induced dielectrophoretic assembly behavior of gold nanoparticles in a wide frequency range

    Liu, Weiyu; Wang, Chunhui; Ding, Haitao; Shao, Jinyou; Ding, Yucheng

    2016-05-01

    In this work, we focus on frequency-dependence of pearl chain formations (PCF) of gold nanoparticles driven by AC dielectrophoresis (DEP), especially in a low field-frequency range, where induced double-layer charging effect at ideally polarizable surfaces on particle DEP behavior and surrounding liquid motion need not be negligible. As field frequency varies, grown features of DEP assembly structures ranging from low-frequency non-bridged gap to high-frequency single gold nanoparticle-made nanowires bridging the electrodes are demonstrated experimentally. Specifically, at 10 kHz, a kind of novel channel-like structure with parallel opposing banks is formed at the center of interelectrode gap. In stark contrast, at 1 MHz, thin PCF with diameter of 100 nm is created along the shortest distance of the isolation spacing. Moreover, a particular conductive path of nanoparticle chains is produced at 1 MHz in a DEP device embedded with multiple floating electrodes. A theoretical framework taking into account field-induced double-layer polarization at both the particle/electrolyte and electrode/electrolyte interface is developed to correlate these experimental observations with induced-charge electrokinetic (ICEK) phenomenon. And a RC circuit model is helpful in accounting for the formation of this particular non-bridged channel-like structure induced by a low-frequency AC voltage. As compared to thin PCF formed at high field frequency that effectively short circuits the electrode pair, though it is difficult for complete PCF bridging to occur at low frequency, the non-bridged conducting microstructure has potential to further miniaturize the size of electrode gap fabricated by standard micromachining process and may find useful application in biochemical sensing.

  1. Flame spread over electrical wire with AC electric fields: Internal circulation, fuel vapor-jet, spread rate acceleration, and molten insulator dripping

    Lim, Seungjae

    2015-04-01

    The effect of electric field on the characteristics of flame spread along a polyethylene (PE) insulated electrical wire was investigated experimentally by varying the AC frequency and voltage applied to the wire. The results showed that the flame spread rate was accelerated due to the convergence of electric flux near the end of wire, having three distinct regimes depending on applied voltage. In each regime, several subregimes could be identified depending on AC frequency. Flame shape (height and width) and slanted direction of the spreading flame were influenced differently. Fuel-vapor jets were ejected from the molten PE surface even for the baseline case without the application of an electric field; this could be attributed to the bursting of fuel vapor bubbles generated from internal boiling at the molten PE surface. An internal circulation of molten-PE was also observed as a result of non-uniform heating by the spreading flame. In the high voltage regime with a high AC frequency, excessive dripping of molten PE led to flame extinction.

  2. Space charge behaviours in polyethylene under combined AC and DC electric fields

    Zhou, Churui; Chen, George

    2014-01-01

    Polyethylene is one of the widely studied polymeric insulation materials, which have been used extensively for cable insulation. One of the major issues related to polymeric materials is its easy formation of space charge, a high chance to cause electric field distortions. This phenomenon is more significant under high voltage direct current (HVDC) stresses. Space charge can also be observed under high voltage alternative current (HVAC)stresses but with much less intensity due to the limited ...

  3. Bridging in contaminated transformer oil under DC and AC electric field

    There are two experimental set up have been established to investigate the bridging effect between two electrodes with different potentials under ac and dc voltages. This paper will explain the full details of the experimental setup and the results. These experiments carried out on pressboard particles under three different levels of ac and dc voltages. Several contamination levels have been investigated. Optical images of particle accumulation have been recorded along with associated conduction current measurement during experiments. At higher voltages the rate of bridge formation is increased along with an associated current increase. The major differences between ac and dc bridges are the shapes of the particle accumulation. The bridge formation rate for ac is slower than dc

  4. Influence of electrical fields (AC and DC) on phytoremediation of metal polluted soils with rapeseed (Brassica napus) and tobacco (Nicotiana tabacum).

    Bi, Ran; Schlaak, Michael; Siefert, Eike; Lord, Richard; Connolly, Helen

    2011-04-01

    The combined use of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. The plants species selected were rapeseed and tobacco. Three kinds of soil were used: un-contaminated soil from forest area (S1), artificially contaminated soil with 15mgkg(-1) Cd (S2) and multi-contaminated soil with Cd, Zn and Pb from an industrial area (S3). Three treatment conditions were applied to the plants growing in the experimental vessels: control (no electrical field), alternating current electrical field (AC, 1Vcm(-1)) and direct current electrical field (DC, 1Vcm(-1)) with switching polarity every 3h. The electrical fields were applied for 30d for rapeseed and 90d for tobacco, each experiment had three replicates. After a total of 90d growth for rapeseed and of 180d for tobacco, the plants were harvested. The pH variation from anode to cathode was eliminated by switching the polarity of the DC field. The plants reacted differently under the applied electrical field. Rapeseed biomass was enhanced under the AC field and no negative effect was found under DC field. However, no enhancement of the tobacco biomass under the AC treatment was found. The DC field had a negative influence on biomass production on tobacco plants. In general, Cd content was higher in both species growing in S2 treated with AC field compared to the control. Metal uptake (Cd, Cu, Zn and Pb) per rapeseed plant shoot was enhanced by the application of AC field in all soils. PMID:21237480

  5. Effect of electric fields on the stabilization of premixed laminar bunsen flames at low AC frequency: Bi-ionic wind effect

    Kim, Minkuk

    2012-03-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally by applying AC electric fields at low frequency below 60. Hz together with DC in the single electrode configuration. The blowoff velocity has been measured for varying AC voltage and frequency. A transition frequency between low and high frequency regimes has been identified near 40-50. Hz, where AC electric fields have minimal effect on flame stabilization. In the low frequency regime, the blowoff velocity decreased linearly with AC voltage such that the flames became less stable. This was consistent with the DC result, implying the influence of the ionic wind effect. The variation of blowoff velocity with AC frequency showed a non-monotonic behavior in that the velocity decreased and then increased, exhibiting minimum blowoff velocity near 6-8. Hz. Based on the molecular kinetic theory, the developing degree of ionic wind was derived. By considering the ionic wind effects arising from both positive and negative ions in a flame zone, the bi-ionic wind effect successfully explained the non-monotonic behavior of blowoff velocity with AC frequency in the low frequency regime. © 2011 The Combustion Institute.

  6. Analytical solutions of ac electrokinetics in interdigitated electrode arrays: Electric field, dielectrophoretic and traveling-wave dielectrophoretic forces

    Sun, Tao; Morgan, Hywel; Green, Nicolas G

    2007-01-01

    Analysis of the movement of particles in a nonuniform field requires accurate knowledge of the electric field distribution in the system. This paper describes a method for analytically solving the electric field distribution above interdigitated electrode arrays used for dielectrophoresis (DEP) and traveling wave dielectrophoresis (twDEP), using the Schwarz-Christoffel mapping method. The electric field solutions are used to calculate the dielectrophoretic force in both cases, and the traveli...

  7. Electrical Characteristics, Electrode Sheath and Contamination Layer Behavior of a Meso-Scale Premixed Methane-Air Flame Under AC/DC Electric Fields

    Chen, Qi; Yan, Limin; Zhang, Hao; Li, Guoxiu

    2016-05-01

    Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC (0-4300 V, 0-500 Hz) and DC (0-3300 V) electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 100-102 μA, the electron density 1015-1016 m‑3 and further the power dissipation ≤ 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10‑4-10‑3 Ω‑1·m‑1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length (31–98 μm) and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process. supported by National Natural Science Foundation of China (No. 51376021), and the Fundamental Research Fund for Major Universities (No. 2013JBM079)

  8. Electro-osmotic flow of a second-grade fluid in a porous microchannel subject to an AC electric field

    MISRA J.C.; CHANDRA S.

    2013-01-01

    Studies on electro-osmotic flows of various types of fluids in microcharmel are of great importance owing to their multifold applications in the transport of liquids,particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field.In the case of viscoelastic fluids,the volumetric flow rate differs significantly from that of Newtonian fluids,even when the flow takes place under the same pressure gradient and the same electric field.With this end in view,this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel,which is under the action of an alternating electric field.The influence of various rheologieal and electro-osmotic parameters,e.g.,the Reynolds number,Debye-Huckel parameter,shape factor and fluid viscoelasticity on the kinematics of the fluid,has been investigated for a second-grade viscoelastic fluid.The problem is first treated by using analytical methods,but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA.The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the Stern and diffuse layers.The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced.The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number.The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations,where electro-osmotic flows come into the picture,as in blood flow in the micro-circulatory system subject to an electric field.

  9. Observation of multi-scale oscillation of laminar lifted flames with low-frequency AC electric fields

    Ryu, Seol

    2010-01-01

    The oscillation behavior of laminar lifted flames under the influence of low-frequency AC has been investigated experimentally in coflow jets. Various oscillation modes were existed depending on jet velocity and the voltage and frequency of AC, especially when the AC frequency was typically smaller than 30 Hz. Three different oscillation modes were observed: (1) large-scale oscillation with the oscillation frequency of about 0.1 Hz, which was independent of the applied AC frequency, (2) small-scale oscillation synchronized to the applied AC frequency, and (3) doubly-periodic oscillation with small-scale oscillation embedded in large-scale oscillation. As the AC frequency decreased from 30 Hz, the oscillation modes were in the order of the large-scale oscillation, doubly-periodic oscillation, and small-scale oscillation. The onset of the oscillation for the AC frequency smaller than 30 Hz was in close agreement with the delay time scale for the ionic wind effect to occur, that is, the collision response time. Frequency-doubling behavior for the small-scale oscillation has also been observed. Possible mechanisms for the large-scale oscillation and the frequency-doubling behavior have been discussed, although the detailed understanding of the underlying mechanisms will be a future study. © 2009 The Combustion Institute.

  10. Bone growth in electric fields

    Research performed in several laboratories has shown that artificially induced currents affect bone growth. Studies of various current characteristics produced by implanted electrodes indicate that continuous dc, interrupted dc, and asymmetric ac all increase osteogenesis at the cathode. Stimulation from an externally applied balanced ac field was reported to reduce bone loss from disuse. The purpose of the study being reported here was to examine the influence of a uniform ac electric field on the normal skeletal growth pattern of rats. Juvenile rats received whole body exposure to uniform, vertical 60-Hz electric fields at 100 kV/m for 30 days. There were no marked alterations in the general growth pattern of the exposed animals compared to controls maintained under similar conditions. Bone growth rate, measured by tetracycline labeling, morphology of lumbar vertebrae and tibias and cortical bone area and marrow space area of tibias were not disturbed by exposure to the electric fields. (author)

  11. Dynamic characteristics of double-barrier nanostructures with asymmetric barriers of finite height and widths in a strong ac electric field

    Chuenkov, V. A., E-mail: v.a.chuenkov@mail.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2013-12-15

    The theory of the interaction of a monoenergetic flow of injected electrons with a strong high-frequency ac electric field in resonant-tunneling diode (RTD) structures with asymmetric barriers of finite height and width is generalized. In the quasi-classical approximation, electron wavefunctions and tunneling functions in the quantum well and barriers are found. Analytical expressions for polarization currents in RTDs are derived in both the general case and in a number of limiting cases. It is shown that the polarization currents and radiation power in RTDs with asymmetric barriers strongly depend on the ratio of the probabilities of electron tunneling through the emitter and collector barriers. In the quantum mode, when δ = ε − ε{sub r} = ħω ≪ Γ (ε is the energy of electrons injected in the RTD, ħ is Planck’s constant, ω is the ac field frequency, ε{sub r} and Γ are the energy and width of the resonance level, respectively), the active polarization current in a field of E ≈ 2.8ħω/ea (e is the electron charge and a is the quantum-well width) reaches a maximum equal in magnitude to 84% of the direct resonant current, if the probability of electron tunneling through the emitter barrier is much higher than that through the collector barrier. The radiation-generation power at frequencies of ω = 10{sup 12}–10{sup 13} s{sup −1} can reach 10{sup 5}–10{sup 6} W/cm{sup 2} in this case.

  12. Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages

    Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using dc voltages (classical electrowetting). Electrical actuation of conducting droplets using ac voltages and the actuation of insulating droplets (using dc or ac voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under ac actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under ac actuation and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. This paper also presents experiments which quantify the influence of the ac frequency and the electrical properties of the droplet on its velocity under electrical actuation. The velocities of droplets moving between two parallel plates under ac actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the ac actuation voltage; the cut-off ac frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for the actuation of droplets in microfluidic applications

  13. ac propulsion system for an electric vehicle

    Geppert, S.

    1980-01-01

    It is pointed out that dc drives will be the logical choice for current production electric vehicles (EV). However, by the mid-80's, there is a good chance that the price and reliability of suitable high-power semiconductors will allow for a competitive ac system. The driving force behind the ac approach is the induction motor, which has specific advantages relative to a dc shunt or series traction motor. These advantages would be an important factor in the case of a vehicle for which low maintenance characteristics are of primary importance. A description of an EV ac propulsion system is provided, taking into account the logic controller, the inverter, the motor, and a two-speed transmission-differential-axle assembly. The main barrier to the employment of the considered propulsion system in EV is not any technical problem, but inverter transistor cost.

  14. AC motor drive system for electric cars

    Morohoshi, Yukinobu; Yoshinori, Naoto; Naito, Hironobu (Fuji Electric Co., Ltd., Tokyo, (Japan))

    1989-08-10

    Various main circuit equipment with large capacity GTO thyristors are outlined for AC and DC electric cars. The configuration of a PWM converter system is presented for the AC main motor drive system of the Shinkansen trains, and its following features are described: the high power factor control capable of keeping a power factor 100% constantly, energy saving by power regenerative braking, the small triple structure with large capacity reverse-conducting GTO thyristors of 4,500V/3,000A, and the reduction of equivalent interfering current and harmonic current by three phase-triple phase difference operation. Furthermore, a control logic equipment with 16 bit MPU and a main transformer are outlined, and the verification test results of the control logic equipment by an analog model simulation and the combinational test results of the commercial equipment are reported. Prototype VVVF inverter system for DC electric cars is also presented. 6 refs., 13 figs., 3 tabs.

  15. AC losses in a HTS coil carrying DC current in AC external magnetic field

    We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field

  16. On the Application of TLS Techniques to AC Electrical Drives

    M. Cirrincione

    2005-03-01

    Full Text Available This paper deals with the application of a new neuron, the TLS EXIN neuron, to AC induction motor drives. In particular, it addresses two important subjects of AC induction motor drives: the on-line estimation of the electrical parameters of the machine and the speed estimation in sensorless drives. On this basis, this work summarizes the parameter estimation and sensorless techniques already developed by the authors over these last few years, all based on the TLS EXIN. With regard to sensorless, two techniques are proposed: one based on the MRAS and the other based on the full-order Luenberger observer. The work show some of the most significant results obtained by the authors in these fields and stresses the important potentiality of this new neural technique in AC induction machine drives.

  17. Electric Field Imaging Project

    Wilcutt, Terrence; Hughitt, Brian; Burke, Eric; Generazio, Edward

    2016-01-01

    NDE historically has focused technology development in propagating wave phenomena with little attention to the field of electrostatics and emanating electric fields. This work is intended to bring electrostatic imaging to the forefront of new inspection technologies, and new technologies in general. The specific goals are to specify the electric potential and electric field including the electric field spatial components emanating from, to, and throughout volumes containing objects or in free space.

  18. Electric fields and electrical insulation

    McAllister, Iain Wilson

    2002-01-01

    The adoption of a field-theoretical approach to problems arising in the framework of electrical insulation is discussed with reference to six main topics, which have been addressed over the last 30 years. These include uniform field electrodes, Green's differential equation, electrode surface...... roughness, induced charge, electrostatic probes, and partial discharge transients, together with several follow-on aspects. Each topic is introduced and thereafter the progress achieved through the use of a field-theoretical approach is reviewed. Because the topics cover a wide spectrum of conditions......, it is amply demonstrated that such an approach can lead to significant progress in many areas of electrical insulation....

  19. An AC electric trap for ground-state molecules

    van Veldhoven, J; Meijer, G; Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Meijer, Gerard

    2005-01-01

    We here report on the realization of an electrodynamic trap, capable of trapping neutral atoms and molecules in both low-field and high-field seeking states. Confinement in three dimensions is achieved by switching between two electric field configurations that have a saddle-point at the center of the trap, i.e., by alternating a focusing and a defocusing force in each direction. AC trapping of 15ND3 molecules is experimentally demonstrated, and the stability of the trap is studied as a function of the switching frequency. A 1 mK sample of 15ND3 molecules in the high-field seeking component of the |J,K>=|1,1> level, the ground-state of para-ammonia, is trapped in a volume of about 1 mm^3.

  20. Electric field analysis

    Chakravorti, Sivaji

    2015-01-01

    This book prepares newcomers to dive into the realm of electric field analysis. The book details why one should perform electric field analysis and what are its practical implications. It emphasizes both the fundamentals and modern computational methods of electric machines. The book covers practical applications of the numerical methods in high voltage equipment, including transmission lines, power transformers, cables, and gas insulated systems.

  1. Electric drives of traction rolling stocks with AC motors

    Leonas Povilas LINGAITIS; Liudvinavičius, Lionginas

    2006-01-01

    The paper considers the variation of circuit design of the electric drives in traction rolling stocks when traditional DC electric machines are replaced with AC electric machines. Simplified circuit diagrams of the electric drives using electric machines of non-commutator type are offered. Operational defects of DC traction engines are weighed against some positive characteristics of direct current series excitation in traction engines, determining their extensive use in the electric drives o...

  2. Pulsed electric fields

    The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...

  3. Dielectrics in electric fields

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  4. A new probe for measuring small electric fields in plasmas

    Stenzel, R. L.

    1991-01-01

    A dipolar double probe has been developed for in situ measurements of small electric fields in laboratory plasmas. The probe measures dc to ac electric fields (f values between 0 and 20 MHz) with high sensitivity (Emin about 10 microV/cm) and responds to both space charge electric fields and inductive electric fields. Using voltage-to-frequency conversion, the probe signal is obtained free of errors and loading effects by a transmission line. Various examples of useful applications for the new probe are presented, such as measurements of dc ambipolar fields, ac space-charge fields of ion acoustic waves, ac inductive fields of whistler waves, and mixed inductive and space-charge electric fields in current-carrying magnetoplasmas.

  5. Electrohydrodynamics of suspension of liquid drops in AC fields

    Abdul Halim, Md.; Esmaeeli, Asghar

    2012-11-01

    Manipulation of liquid drops by an externally applied electric field is currently the focus of increased attention because of its relevance in a broad range of industrial processes. The effect of a uniform DC electric field on a solitary drop is well studied; however, less is know about the impact of electric field on suspension of liquid drops, and very little information is available on the impact of AC field on a single or a suspension of drops. Here we report the results of Direct Numerical Simulations of electrohydrodynamics of suspension of liquid drops. The governing equations are solved using a front tracking/finite difference technique, in conjunction with Taylor's leaky dielectric model. The imposed electric potential comprises of two parts, a time-independent base and a time-dependent part. The goal is to explore the relative importance of these two components in setting the statistically steady state behavior of the suspension. To this end, we report the results of three sets of simulations, where (i) the time-dependent part act as a perturbation on the base potential, (ii) the two components are of the same order, and (iii) the time-dependent part is much larger than the base potential. The problem is studied as a function of the governing nondimensional parameters.

  6. EHV AC undergrounding electrical power performance and planning

    Benato, Roberto

    2010-01-01

    EHV AC Undergrounding Electrical Power discusses methods of analysis for cable performance and for the behaviour of cable, mixed and overhead lines. The authors discuss the undergrounding of electrical power and develop procedures based on the standard equations of transmission lines. They also provide technical and economical comparisons of a variety of cables and analysis methods, in order to examine the performance of AC power transmission systems. A range of topics are covered, including: energization and de-energization phenomena of transmission lines; power quality; and cable safety cons

  7. Transcranial Electric Field Stimulation

    Arfaee, Arash

    2015-01-01

    Nervous stimulation with electric methods not only has a long history in the treatment of many conditions but also in the last two decades has been used increasingly as a powerful functional brain mapping tool alongside other imaging techniques. This technology has been used to record the stimulation-evoked activity of the stimulated location. This research describes work surrounding a novel technique for brain and nervous stimulation using the electric field as the medium; particularly tra...

  8. Heat Transfer Analysis for Industrial AC Electric Arc Furnace

    (U)nal (C)amdali; Murat Tun(c)

    2005-01-01

    The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some suggestions about decreasing heat losses were presented.

  9. Performance testing of the AC propulsion ELX electric vehicle

    Kramer, W.E.; MacDowall, R.D.; Burke, A.F.

    1994-06-01

    Performance testing of the AC Propulsion ELX electric vehicle is described. Test data are presented and analyzed. The ELX vehicle is the first of a series of electric vehicles of interest to the California Air Resources Board. The test series is being conducted under a Cooperative Research and Development Agreement (CRADA) between the US Department of energy and the California Air Resources Board. The tests which were conducted showed that the AC Propulsion ELX electric vehicle has exceptional acceleration and range performance. when the vehicle`s battery was fully charged, the vehicle can accelerate from 0 to 96 km/h in about 10 seconds. Energy consumption and range tests using consecutive FUDS and HWFET Driving cycles (the all-electric cycle) indicate that the energy economy of the AC Propulsion ELX electric vehicle with regenerative braking is 97 W{center_dot}h/km, with a range of 153 km (95 miles). Computer simulations performed using the SIMPLEV Program indicate that the vehicle would have a range of 327 km (203 miles) on the all-electric cycle if the lead acid batteries were replaced with NiMH batteries having an energy density of 67 W{center_dot}h/kg. Comparisons of FUDS test data with and without regenerative braking indicated that regenerative braking reduced the energy consumption of the ELX vehicle by approximately 25%.

  10. Influence of the uniform electric field on viscosity of magnetic nanofluid (Fe3O4-EG)

    Monajjemi Rarani, E.; Etesami, N.; Nasr Esfahany, M.

    2012-11-01

    Viscosity of Fe3O4/ethylene glycol nanofluids under electric field (ac and dc) was investigated experimentally. Magnetic nanofluids were prepared by dispersing Fe3O4 nanoparticles in ethylene glycol using a sonicator. Experiments showed that dilute magnetic nanofluids (fluid exhibit Newtonian behavior. Viscosity of Fe3O4 / ethylene glycol nanofluids in electric field was measured using capillary tube viscometer. Electric field decreased the viscosity of magnetic nanofluids and base fluid. The viscosity reduction was more profound in higher volume concentrations of nanoparticles. dc electric field caused greater viscosity reduction in magnetic nanofluids relative to ac electric field while ac electric field showed greater reduction effect for base liquid.

  11. DIAGNOSTIC FEATURES RESEARCH OF AC ELECTRIC POINT MOTORS

    S. YU. Buryak

    2014-05-01

    Full Text Available Purpose.Considerable responsibility for safety of operation rests on signal telephone and telegraph department of railway. One of the most attackable nodes (both automation systems, and railway in whole is track switches. The aim of this investigation is developing such system for monitoring and diagnostics of track switches, which would fully meet the requirements of modern conditions of high-speed motion and heavy trains and producing diagnostics, collection and systematization of data in an automated way. Methodology. In order to achieve the desired objectives research of a structure and the operating principle description of the switch electric drive, sequence of triggering its main units were carried out. The operating characteristics and settings, operating conditions, the causes of failures in the work, andrequirements for electric drives technology and their service were considered and analyzed. Basic analysis principles of dependence of nature of the changes the current waveform, which flows in the working circuit of AC electric point motor were determined. Technical implementation of the monitoring and diagnosing system the state of AC electric point motors was carried out. Findings. Signals taken from serviceable and defective electric turnouts were researched. Originality. Identified a strong interconnectionbetween the technical condition of the track switchand curve shape that describes the current in the circuit of AC electric point motor during operation which is based on the research processes that have influence on it during operation. Practical value. Shown the principles of the technical approach to the transition from scheduled preventive maintenance to maintenance of real condition for a more objective assessment and thus more rapid response to emerging or failures when they occur gradually, damages and any other shortcomings in the work track switch AC drives.

  12. Measurement of the efficiency of cell membrane electroporation using pulsed ac fields

    Electroporation is a long-established technique used to deliver molecules to cells. Most in vivo electroporation protocols entail applying square-wave, or monotonically-decreasing pulses but relatively few have explored the use of pulsed ac fields. This study measures the efficiency of electroporation in human kidney embryonal cells, using pulsed ac electric fields of peak amplitude 30-200 kV m-1. The results indicate that optimum electroporation efficiencies of up to 70% can be achieved using pulses at frequencies of 20-160 kHz. Increasing the field strength results in higher electroporation efficiency, but also increases cell kill. This study confirms that efficient electroporation may be achieved using pulsed ac fields. This finding raises the possibility of a wider range of clinical and laboratory applications based on ac technology and avoiding the use of invasive needle electrodes

  13. Electroporation of cells using EM induction of ac fields by a magnetic stimulator

    This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m-1. Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use of pulsed ac fields. Following our previous study, which established the effectiveness of ac fields for electroporating cell membranes, a primary/secondary coil system was constructed to produce sufficiently strong electric fields by electromagnetic induction. The primary coil was formed from the applicator of an established transcranial magnetic stimulation (TMS) system, while the secondary coil was a purpose-built device of a design which could eventually be implanted into tissue. The effects of field strength, pulse interval and cumulative exposure time were investigated using microscopy and flow cytometry. Results from experiments on concentrated cell suspensions showed an optimized electroporation efficiency of around 50%, demonstrating that electroporation can be practicably achieved by inducing such pulsed ac fields. This finding confirms the possibility of a wide range of in vivo applications based on magnetically coupled ac electroporation.

  14. 交直流叠加电场下油纸绝缘的油流带电特性%Flow Electrification Characteristics of Oil-Paper Insulation under AC Superimposed DC Electric Field

    陈庆国; 高源; 池明赫; 林林

    2014-01-01

    为研究叠加电场作用下油纸绝缘的油流带电特性,在实验室搭建了同轴圆柱电极结构的油纸绝缘模型,利用密闭油循环系统开展了叠加电场下油流带电的试验研究,并探讨了外施电压幅值、直流分量比例和油流速度对油流带电的影响。试验结果表明,流速和外施电压幅值对冲流电流的影响与温度有关。在低温下冲流电流随流速和外施电压幅值线性增加,提高直流分量比例会促进冲流电流;在高温下冲流电流随流速指数增加,随外施电压幅值提高出现峰值,峰值电压随直流分量比例提高而下降。理论分析表明:较低温度下油中冲流电流大小取决于纸中负离子的迁移和扩散速度;而在较高温度下该冲流电流取决于油流剥离正离子的速度和外电极处电荷泄放的速率;温度通过影响绝缘中离子迁移速度和电场分布而影响油流带电特性。%In order to investigate the flow electrification characteristics of oil-paper insulation under the AC superimposed DC electric field, an oil-paper tube model with concentric cylindrical electrode geometry was built in laboratory. Experiment study on flow electrification under AC superimposed DC electric field was carried out with the closed oil circulating system, and the influence of voltage amplitude, DC component ratio and oil flow velocity on flow electrification was discussed. The experiment results show that the influences of oil flow velocity and the amplitude of applied voltage on streaming currents are related to temperature. At low temperature, the streaming current increases linearly with flow velocity and amplitude of applied voltage, and the increase of the DC component ratio can enhance the streaming current. At high temperature, the streaming current increases exponentially with flow velocity and shows peak effect with amplitude of applied voltage. The peak point voltage decreases with the DC

  15. Electric charge in the stochastic electric field

    Simonov, Yu A

    2016-01-01

    The influence of electric stochastic fields on the relativistic charged particles is investigated in the gauge invariant path integral formalism. Using the cumulant expansion one finds the exponential relaxation of the charge Green's function both for spinless and Dirac charges.

  16. A PWM transistor inverter for an ac electric vehicle drive

    Slicker, J. M.

    1981-01-01

    A prototype system consisting of closely integrated motor, inverter, and transaxle has been built in order to demonstrate the feasibility of a three-phase ac transistorized inverter for electric vehicle applications. The microprocessor-controlled inverter employs monolithic power transistors to drive an oil-cooled, three-phase induction traction motor at a peak output power of 30 kW from a 144 V battery pack. Transistor safe switching requirements are discussed, and a circuit is presented for recovering trapped snubber inductor energy at transistor turn-off.

  17. Long-range response in ac electricity grids.

    Jung, Daniel; Kettemann, Stefan

    2016-07-01

    Local changes in the topology of electricity grids can cause overloads far away from the disturbance [D. Witthaut and M. Timme, Eur. Phys. J. B 86, 377 (2013)EPJBFY1434-602810.1140/epjb/e2013-40469-4], making the prediction of the robustness against changes in the topology-for example, caused by power outages or grid extensions-a challenging task. The impact of single-line additions on the long-range response of dc electricity grids has recently been studied [D. Labavić, R. Suciu, H. Meyer-Ortmanns, and S. Kettemann, Eur. Phys. J.: Spec. Top. 223, 2517 (2014)1951-635510.1140/epjst/e2014-02273-0]. By solving the real part of the static ac load flow equations, we conduct a similar investigation for ac grids. In a regular two-dimensional grid graph with cyclic boundary conditions, we find a power law decay for the change of power flow as a function of distance to the disturbance over a wide range of distances. The power exponent increases and saturates for large system sizes. By applying the same analysis to the German transmission grid topology, we show that also in real-world topologies a long-ranged response can be found. PMID:27575148

  18. Effect of applied DC electric fields in flame spread over polyethylene-coated electrical wire

    Jin, Young Kyu

    2011-03-01

    We experimentally investigated the effect of applied DC electric fields on the flame spread over polyethylene-coated electrical wire. The flame-spread rates over electrical wire with negative and positive DC electric fields from 0 to ±7 kV were measured and analyzed. We compared the results for DC electric fields with previous results for AC electric fields. We explored whether or not various flame shapes could be obtained with DC electric fields and the main reason for the flame-spread acceleration, particularly at the end of the electrical wire, for AC electric fields. We found that DC electric fields do not significantly affect the flame-spread rates. However, the flame shape is mildly altered by the ionic wind effect even for DC electric fields. The flame-spread rate is relevant to the flame shape and the slanted direction in spite of the mild impact. A possible explanation for the flame spread is given by a thermal-balance mechanism and fuel-vapor jet. © 2011 The Korean Society of Mechanical Engineers.

  19. Electric field gradients in metals

    A review of the recent works on electric field gradient in metals is given. The main emphasis is put on the temperature dependence of the electric field gradient in nonmagnetic metals. Some methods of investigation of this effect using nuclear probes are described. One of them is nuclear accoustic resonance method. (S.B.)

  20. Cryosurgery with pulsed electric fields.

    Charlotte S Daniels

    Full Text Available This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused

  1. Exchange anisotropy determined by magnetic field dependence of ac susceptibility

    Rodríguez-Suárez, R. L.; Vilela Leão, L. H.; de Aguiar, F. M.; Rezende, S. M.; Azevedo, A.

    2003-10-01

    ac susceptibility measurements of ferromagnetic/antiferromagnetic (FM/AF) bilayers are usually performed as a function of the temperature. In this work we describe measurements of transverse biased ac susceptibility (χt) of FM/AF bilayers as a function of the applied magnetic field H0. The measurements were carried out at room temperature by means of an ac magneto-optical Kerr effect susceptometer. The χt-1(H0) dependence, at the saturation magnetization regime, exhibits a linear behavior with the applied field parallel and perpendicular to the exchange bias direction. The linear extrapolation of χt-1 versus H0 cuts the abscissa at asymmetrical values of field due to the exchange bias coupling. The inverse susceptibility is calculated in the saturation regime by a model, which takes into account the free energy of both layers plus a term corresponding to the interfacial coupling. The exchange coupling field (HE) and uniaxial anisotropy (HU) are extracted from the best fit to the experimental results. The results obtained are crosschecked by those obtained from ferromagnetic resonance (FMR) and dc magnetometry. The measurements of the exchange bias and the uniaxial field in all of the three analyzed bilayers gave values that are consistently lower when measured by FMR than those obtained by ac and dc magnetometry. It is argued that the apparently discrepant values of HE and HU, obtained by different techniques, might be explained by existence of unstable AF grains at the AF/FM interface.

  2. A novel high-sensitivity electrostatic biased electric field sensor

    Huang, Jing'ao; Wu, Xiaoming; Wang, Xiaohong; Yan, Xiaojun; Lin, Liwei

    2015-09-01

    In this paper, an electric field sensor (EFS) with high sensitivity is proposed for low-frequency weak-strength ac electric field (E-field) measurements. The EFS is based on a piezoelectric cantilever biased by a strong electrostatic field. The electrostatic bias can enhance the electric field force of a weak ac E-field, thus the cantilever can oscillate in a weak ac E-field and the device sensitivity improves. Theoretical analyses have been established and suggest that a stronger strength of electrostatic field bias would produce a higher sensitivity improvement. In the experiment, a demonstrated sensor consisting of a polyvinylidene fluoride (PVDF) piezoelectric cantilever and a polytetrafluoroethylene (PTFE) electret was built and tested. Instead of extra voltage sources, the PTFE electret was charged to provide the electrostatic field, allowing the EFS a low energy consumption and a simple electric circuit design. The experiment results show good agreement with the simulation. The sensitivity of the cantilever E-field sensor reached 0.84 mV (kV/m)-1 when the surface potential of the electret was  -770 V.

  3. A novel high-sensitivity electrostatic biased electric field sensor

    In this paper, an electric field sensor (EFS) with high sensitivity is proposed for low-frequency weak-strength ac electric field (E-field) measurements. The EFS is based on a piezoelectric cantilever biased by a strong electrostatic field. The electrostatic bias can enhance the electric field force of a weak ac E-field, thus the cantilever can oscillate in a weak ac E-field and the device sensitivity improves. Theoretical analyses have been established and suggest that a stronger strength of electrostatic field bias would produce a higher sensitivity improvement. In the experiment, a demonstrated sensor consisting of a polyvinylidene fluoride (PVDF) piezoelectric cantilever and a polytetrafluoroethylene (PTFE) electret was built and tested. Instead of extra voltage sources, the PTFE electret was charged to provide the electrostatic field, allowing the EFS a low energy consumption and a simple electric circuit design. The experiment results show good agreement with the simulation. The sensitivity of the cantilever E-field sensor reached 0.84 mV (kV/m)−1 when the surface potential of the electret was  −770 V. (paper)

  4. Introducing electric fields

    Roche, John

    2016-09-01

    The clear introduction of basic concepts and definitions is crucial for teaching any topic in physics. I have always found it difficult to teach fields. While searching for better explanations I hit on an approach of reading foundational texts and electromagnetic textbooks in ten year lots, ranging from 1840 to the present. By combining this with modern techniques of textual interpretation I attempt to clarify three introductory concepts: how the field is defined; the principle of superposition and the role of the electrostatic field in a circuit.

  5. Effect of the ac field on a single-molecule magnet bridged between conducting leads

    We study quantum spin-rotation effects for a single-molecule magnet bridged between two conducting leads in the ac and dc magnetic fields. The Landau-Zener dynamics induced by the magnetic field generates mechanical torque, making the molecule to oscillate. This mechanical motion of the molecule exhibits unique features that can be detected by measuring the electronic tunneling current through the molecule. - Highlights: → Magnetic molecules (MM) have been proposed as ultimate units of magnetic memory. → Several experiments were performed to measure electric current through a single molecule. → We study mechanical vibrations of a MM bridged between two leads in the presence of ac and dc fields. → Through quantum spin-rotation coupling such fields generate mechanical motion of the molecule. → The twist of the molecule can be detected by measuring the tunneling current through the molecule.

  6. High benefits approach for electrical energy conversion in electric vehicles from DC to PWM-AC without any generated harmonic

    Highlights: • Novel hybrid power source including AC feature for using in electric/hybrid vehicles. • Minimizing the energy loss in electric/hybrid vehicles by using the proposed system. • Suitable AC wave form for braking/accelerating purposes in electric/hybrid vehicles. • A novelty is that the harmonic generated by the added AC feature is really zero. • Another novelty is the capability of choosing arbitrary frequency for AC feature. - Abstract: This paper presents a novel hybrid power source, including a Li-ion battery together with an interface, which generates simultaneously electrical energy with the forms of both DC and AC for electric vehicles. A novel and high benefits approach is applied to convert the electrical energy of the Li-ion battery from DC form to single-phase symmetric pulse-width modulation (PWM)-AC form. Harmonic generation is one of the important problems when electrical energy is converted from DC to AC but there are not any generated harmonic during the DC/AC conversion using the proposed technique. The proposed system will be widely used in electric/hybrid vehicles because it has many benefits. Minimizing the energy loss (saving energy), no generated harmonic (it is really zero), the capability of arbitrary/necessary frequency selection for output AC voltage and the ability of long distance energy transmission are some novelties and advantages of the proposed system. The proposed hybrid power source including DC/AC PWM inverter is simulated in Proteus 6 software environment and a laboratory-based prototype of the hybrid power source is constructed to validate the theoretical and simulation results. Simulation and experimental results are presented to prove the superiority of the proposed hybrid power supply

  7. What Are Electric and Magnetic Fields? (EMF)

    ... Experiments Stories Lessons Topics Games Activities Lessons MENU What are Electric and Magnetic Fields? (EMF) Kids Homepage ... electric power is something we take for granted. What are electric and magnetic fields? Electric and magnetic ...

  8. Fusion of bacterial spheroplasts by electric fields.

    Ruthe, H J; Adler, J

    1985-09-25

    Spheroplasts of Escherichia coli or Salmonella typhimurium were found to fuse in an electric field. We employed the fusion method developed by Zimmermann and Scheurich (1981): Close membrane contact between cells is established by dielectrophoresis (formation of chains of cells by an a.c. field), then membrane fusion is induced by the application of short pulses of direct current. Under optimum conditions the fusion yield was routinely 90%. Fusable spheroplasts were obtained by first growing filamentous bacteria in the presence of cephalexin, then converting these to spheroplasts by the use of lysozyme. The fusion products were viable and regenerated to the regular bacterial form. Fusion of genetically different spheroplasts resulted in strains of bacteria possessing a combination of genetic markers. Fusion could not be achieved with spheroplasts obtained by growing the cells in the presence of penicillin or by using lysozyme on bacteria of usual size. PMID:3899175

  9. THOR Electric Field Instrument - EFI

    Khotyaintsev, Yuri; Bale, Stuart D.; Bonnell, John W.; Lindqvist, Per-Arne; Phal, Yamuna; Rothkaehl, Hanna; Soucek, Jan; Vaivads, Andris; Åhlen, Lennart

    2016-04-01

    Turbulence Heating ObserveR (THOR) is the first mission ever flown in space dedicated to plasma turbulence. The Electric Field Instrument (EFI) will measure the vector electric field from 0 to 200 kHz. EFI consists of two sets of sensors: Spin-plane Double Probes (EFI-SDP) providing high sensitivity DC electric field in the spacecraft spin plane (2D), and the High-Frequency Antenna (EFI-HFA) providing 3D electric field at frequencies above ~1 kHz. EFI-SDP consists of 4 biased spherical probes extended on 50 m long wire booms, 90 degrees apart in the spin plane, giving a 100 m baseline for each of the two spin-plane electric field components. EFI-HFA consists of 6 x 1.25 m long monopoles, forming 3 dipolar antennas crossed at 90 degrees to each other. In addition to the sensors, EFI contains HFA and SDP pre-amplifiers, as well as bias electronics boards (BEBs) hosted in the man electronics box of the Field and Wave processor (FWP). As THOR spacecraft has a sun-pointing spin axis, EFI-SDP measures the electric field in the plane approximately orthogonal to the sun using long wire booms. The sun-pointing attitude greatly reduces errors due to wake effects and asymmetric photoelectron clouds, enabling the highly accurate in comparison to earlier missions ±0.1 mV/m near-DC electric field measurements. Interferometry using the electric field probes can be used to infer wavelengths and scale sizes at the smallest scales in the plasma. EFI also measures the floating potential of the satellite, which can be used to estimate the plasma density at very high time resolution (up to a few hundred Hz). The sun-pointing attitude greatly reduces changes in the illuminated area, and hence the associated spin-dependent errors. In combination with densities derived from the observed plasma frequency emission line, EFI monitors the plasma density from DC to a few hundred Hz. EFI measurements characterize electric field and density variations associated with kinetic scale plasma

  10. Electric fields and quantum wormholes

    Engelhardt, Dalit; Freivogel, Ben; Iqbal, Nabil

    2015-09-01

    Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole." We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a nonperturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U (1 ) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter.

  11. Electric fields and quantum wormholes

    Engelhardt, Dalit; Iqbal, Nabil

    2015-01-01

    Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole". We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a non-perturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U(1) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter.

  12. SQUIDs De-fluxing Using a Decaying AC Magnetic Field

    Matlashov, Andrei Nikolaevich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Semenov, Vasili Kirilovich [State Univ. of New York (SUNY), Plattsburgh, NY (United States); Anderson, Bill [Senior Scientific, LLC, Albuquerque, NM (United States)

    2016-06-08

    Flux trapping is the Achilles’ heel of all superconductor electronics. The most direct way to avoid flux trapping is a prevention of superconductor circuits from exposure to magnetic fields. Unfortunately this is not feasible if the circuits must be exposed to a strong DC magnetic field even for a short period of time. For example, such unavoidable exposures take place in superparamagnetic relaxation measurements (SPMR) and ultra-low field magnetic resonance imaging (ULF MRI) using unshielded thin-film SQUID-based gradiometers. Unshielded SQUIDs stop working after being exposed to DC magnetic fields of only a few Gauss in strength. In this paper we present experimental results with de-fluxing of planar thin-film LTS SQUID-based gradiometers using a strong decaying AC magnetic field. We used four commercial G136 gradiometers for SPMR measurements with up to a 10 mT magnetizing field. Strong 12.9 kHz decaying magnetic field pulses reliably return SQUIDs to normal operation 50 ms after zeroing the DC magnetizing field. This new AC de-fluxing method was also successfully tested with seven other different types of LTS SQUID sensors and has been shown to dissipate extremely low energy.

  13. On Conformal Field Theories With Extremal a/c Values

    Zhiboedov, Alexander

    2013-01-01

    Unitary conformal field theories (CFTs) are believed to have positive (non-negative) energy correlators. Energy correlators are universal observables in higher-dimensional CFTs built out of integrated Wightman functions of the stress-energy tensor. We analyze energy correlators in parity invariant four-dimensional CFTs. The goal is to use the positivity of energy correlators to further constrain unitary CFTs. It is known that the positivity of the simplest one-point energy correlator implies that 1/3 <= a/c <= 31/18 where a and c are the Weyl anomaly coefficients. We use the positivity of higher point energy correlators to show that CFTs with extremal values of a/c have trivial scattering observables. More precisely, for a/c=1/3 and a/c=31/18 all energy correlators are fixed to be the ones of the free boson and the free vector theory correspondingly. Similarly, we show that the positivity and finiteness of energy correlators together imply that the three-point function of the stress tensor in a CFT cann...

  14. AC electric motors control advanced design techniques and applications

    Giri, Fouad

    2013-01-01

    The complexity of AC motor control lies in the multivariable and nonlinear nature of AC machine dynamics. Recent advancements in control theory now make it possible to deal with long-standing problems in AC motors control. This text expertly draws on these developments to apply a wide range of model-based control designmethods to a variety of AC motors. Contributions from over thirty top researchers explain how modern control design methods can be used to achieve tight speed regulation, optimal energetic efficiency, and operation reliability and safety, by considering online state var

  15. Study of AC electrical conduction mechanisms in an epoxy polymer

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-11-01

    The AC conductivity of an epoxy resin was investigated in the frequency range 10^{-1} - 106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σ_{ac} was described by the law: σ_{ac}=ω \\varepsilon0\\varepsilon^''_{HN}+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C).

  16. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  17. AC losses and transient field stability of PF-FSJS sample

    This series of 17 slides deals with AC losses and transient field stability of poloidal field full-size-joint sample) which is relevant to the poloidal field coils of ITER. The topic is divided into 6 parts: 1) general - AC losses, 2) conductor magnetization, 3) conductor calorimetry, 4) conclusion on AC losses, 5) stability, and 6) conclusion on stability

  18. AC losses and transient field stability of PF-FSJS sample

    Zani, L

    2003-07-01

    This series of 17 slides deals with AC losses and transient field stability of poloidal field full-size-joint sample) which is relevant to the poloidal field coils of ITER. The topic is divided into 6 parts: 1) general - AC losses, 2) conductor magnetization, 3) conductor calorimetry, 4) conclusion on AC losses, 5) stability, and 6) conclusion on stability.

  19. On conformal field theories with extremal (a/c) values

    Unitary conformal field theories (CFTs) are believed to have positive (non-negative) energy correlators. Energy correlators are universal observables in higher-dimensional CFTs built out of integrated Wightman functions of the stress-energy tensor. We analyze energy correlators in parity invariant four-dimensional CFTs. The goal is to use the positivity of energy correlators to further constrain unitary CFTs. It is known that the positivity of the simplest one-point energy correlator implies that (1/3)≤(a/c)≤(31/18) where a and c are the Weyl anomaly coefficients. We use the positivity of higher point energy correlators to show that CFTs with extremal values of (a/c) have trivial scattering observables. More precisely, for (a/c)=(1/3) and (a/c)=(31/18) all energy correlators are fixed to be the ones of the free boson and the free vector theory correspondingly. Similarly, we show that the positivity and finiteness of energy correlators together imply that the three-point function of the stress tensor in a CFT cannot be proportional to the one in the theory of free boson, free fermion or free vector field

  20. Linear electric field mass spectrometry

    McComas, David J.; Nordholt, Jane E.

    1992-01-01

    A mass spectrometer and methods for mass spectrometry. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field.

  1. Special Effect of Parallel Inductive Electric Field

    陈涛; 刘振兴; W.Heikkila

    2002-01-01

    Acceleration of electrons by a field-aligned electric field during a magnetospheric substorm in the deep geomagnetic tail is studied by means of a one-dimensional electromagnetic particle code. It was found that the free acceleration of the electrons by the parallel electric field is obvious; kinetic energy variation is greater than electromagnetic energy variation in the presence of parallel electric field. Magnetic energy is greater than kinetic energy variation and electric energy variation in the absence of the parallel electric field. More wave modes in the presence of the parallel electric field are generated than those in the absence of the parallel electric field.

  2. Nanoconfined water under electric field

    Luzar, Alenka; Bratko, D.; Daub, C. D.

    2010-03-01

    We study the effect of electric field on interfacial tension of nanoconfined water [1,2] using molecular simulations. Our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale hydrophobic channels and nanoporous materials [3]. We suggest a new mechanism to orient nanoparticles by an applied electric field even when the particles carry no charges or dipoles of their own. Coupling to the field can be accomplished trough solvent-mediated interaction between the electric field and a nanoparticle [4]. For nanoscale particles in water, we find the response to the applied field to be sufficiently fast to make this mechanism relevant for biological processes, design of novel nanostructures and sensors, and development of nanoengineering methods [5]. [1]C. D. Daub, D. Bratko, K. Leung and A. Luzar, J. Phys. Chem. C 111, 505 (2007). [2] D. Bratko, C. D. Daub, K. Leung and A. Luzar, J. Am. Chem. Soc. 129, 2504 (2007) [3] D. Bratko, C. D. Daub and A. Luzar, Phys. Chem. Chem. Phys. 10, 6807 (2008). [4] D. Bratko, C. D. Daub and A. Luzar, Faraday Discussions 141, 55 (2009). [5] C. D. Daub, D. Bratko, T. Ali and A. Luzar, Phys. Rev. Lett. 103, 207801 (2009).

  3. Combination of ac electroosmosis and dielectrophoresis for particle manipulation on electrically-induced microscale wave structures

    Chung, Cheng-Che; Glawdel, Tomasz; Ren, Carolyn L.; Chang, Hsien-Chang

    2015-03-01

    This work presents a simple method to fabricate controllable microscale wave structures on the top of regular interdigitated electrode (IDE) arrays using electrically-assisted lithography techniques. Smooth wave structures are extremely difficult, if not impossible, to fabricate using traditional multilayer photolithography technology. The fabricated wave structures were carefully measured using an optical profiler and the measured wave profiles were used in the numerical simulation of electrical field and for evaluating the parameters influencing the fabricated wave structure. It is demonstrated that the combined smooth wave structure and IDE array offer unique capability for particle manipulation including particle concentration, aggregation and separation. Particle motion manipulated via the combined wave structure and IDE array is governed by ac electroosmosis (ACEO), dielectrophoresis (DEP) or a combination of both depending on the applied frequency. At lower frequencies (~30 kHz), ACEO dominates and particles are driven to move along the valleys of the wave structures; while at higher frequencies (~200 kHz), DEP force dominates which concentrates particles at the peaks of the wave structures. In addition, varying the ac waveform from sine-wave to square-wave allows for dynamic control of particle motion. Size-dependent particle separation over the wave structure is also demonstrated for a mixture of 0.5 µm and 2 µm particles that are separated into two populations by the joint effects of drag and DEP forces when being pumped to flow via ACEO.

  4. Combination of ac electroosmosis and dielectrophoresis for particle manipulation on electrically-induced microscale wave structures

    This work presents a simple method to fabricate controllable microscale wave structures on the top of regular interdigitated electrode (IDE) arrays using electrically-assisted lithography techniques. Smooth wave structures are extremely difficult, if not impossible, to fabricate using traditional multilayer photolithography technology. The fabricated wave structures were carefully measured using an optical profiler and the measured wave profiles were used in the numerical simulation of electrical field and for evaluating the parameters influencing the fabricated wave structure. It is demonstrated that the combined smooth wave structure and IDE array offer unique capability for particle manipulation including particle concentration, aggregation and separation. Particle motion manipulated via the combined wave structure and IDE array is governed by ac electroosmosis (ACEO), dielectrophoresis (DEP) or a combination of both depending on the applied frequency. At lower frequencies (∼30 kHz), ACEO dominates and particles are driven to move along the valleys of the wave structures; while at higher frequencies (∼200 kHz), DEP force dominates which concentrates particles at the peaks of the wave structures. In addition, varying the ac waveform from sine-wave to square-wave allows for dynamic control of particle motion. Size-dependent particle separation over the wave structure is also demonstrated for a mixture of 0.5 µm and 2 µm particles that are separated into two populations by the joint effects of drag and DEP forces when being pumped to flow via ACEO. (paper)

  5. Nonpremixed flame in a counterflow under electric fields

    Park, Daegeun

    2016-05-08

    Electrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could

  6. Lattice QCD with strong external electric fields

    Yamamoto, Arata

    2012-01-01

    We study particle generation by a strong electric field in lattice QCD. To avoid the sign problem of the Minkowskian electric field, we adopt the "isospin" electric charge. When a strong electric field is applied, the insulating vacuum is broken down and pairs of charged particles are produced by the Schwinger mechanism. The competition against the color confining force is also discussed.

  7. Spin-polarized currents in double and triple quantum dots driven by ac magnetic fields

    Busl, Maria; Platero, Gloria

    2010-01-01

    We analyze transport through both a double quantum dot and a triple quantum dot with inhomogeneous Zeeman splittings in the presence of crossed dc and ac magnetic fields. We find that strongly spin-polarized current can be achieved by tuning the relative energies of the Zeeman-split levels of the dots, by means of electric gate voltages: depending on the energy level detuning, the double quantum dot works either as spin-up or spin-down filter. We show that a triple quantum dot in series under...

  8. Nonlinear dynamics of Josephson vortices in a film screen under dc and ac magnetic fields

    Sheikhzada, Ahmad; Gurevich, Alexander

    2014-01-01

    We present detailed numerical simulations of Josephson vortices in a long Josephson junction perpendicular to a thin film screen under strong dc and ac magnetic fields. By solving the sine-Gordon equation, we calculated the threshold magnetic field for penetration of fluxons as a function of frequency, and the power dissipated by oscillating fluxons as functions of the ac field amplitude and frequency. We considered the effects of superimposed ac and dc fields, and a bi-harmonic magnetic fiel...

  9. Localization in an external electric field

    Bleibaum, O.; Belitz, D.

    2003-01-01

    The impact of an electric field on the electron localization problem is studied within the framework of a field-theoretic formulation. The investigation shows that the impact of the electric field on the localization corrections is governed by the interplay between two time scales, one set by the electric field, and the other by the phase relaxation rate. At very low temperatures the scaling of the conductivity is governed by the electric field. In this regime the conductivity depends logarit...

  10. AC electrical conductivity of poly(methyl methacrylate)/carbon black composite

    The study deals with the ac electrical conduction of poly(methyl methacrylate)/carbon black composite of different carbon black (CB) filler concentrations (2, 6, 12 wt%). The ac electrical conductivity was studied as a function of filler concentration, frequency in the range from 100 kHz to 2 MHz, and temperature in the range from 300 to 450 K. It was found that ac electrical conductivity increases by increasing both temperature and CB concentration. The observed overall mechanism of electrical conduction has been related to the transfer of electrons through the CB aggregations distributed in the polymer matrix. The observed increase in conductivity with CB concentration was interpreted through the percolation theory

  11. GROUNDWATER AND SOIL REMEDIATION USING ELECTRICAL FIELD

    Enhancements of contaminants removal and degradation in low permeability soils by electrical fields are achieved by the processes of electrical heating, electrokinetics, and electrochemical reactions. Electrical heating increases soil temperature resulting in the increase of cont...

  12. A Boundary Element Solution to the Problem of Interacting AC Fields in Parallel Conductors

    Einar M. Rønquist

    1984-04-01

    Full Text Available The ac fields in electrically insulated conductors will interact through the surrounding electromagnetic fields. The pertinent field equations reduce to the Helmholtz equation inside each conductor (interior problem, and to the Laplace equation outside the conductors (exterior problem. These equations are transformed to integral equations, with the magnetic vector potential and its normal derivative on the boundaries as unknowns. The integral equations are then approximated by sets of algebraic equations. The interior problem involves only unknowns on the boundary of each conductor, while the exterior problem couples unknowns from several conductors. The interior and the exterior problem are coupled through the field continuity conditions. The full set of equations is solved by standard Gaussian elimination. We also show how the total current and the dissipated power within each conductor can be expressed as boundary integrals. Finally, computational results for a sample problem are compared with a finite difference solution.

  13. AC electric sensing of slug-flow properties with exposed gold microelectrodes

    A new method for slug-flow (segmented flow) characterization by means of ac electric sensing is proposed. Water segments regularly dispersed in kerosene are used as an experimental system. The sensing procedure is carried out in a plexiglass microchip with embedded gold microelectrodes. The presence of passing slugs over a measurement spot is determined from impedance variations. A square-shaped signal resulting from the slug flow is acquired and flow properties such as the mean velocity and length of the slugs are calculated. Complex behaviour of the corresponding electrochemical system is studied. Dependence of the impedance signal on the flow rate, ion concentration in the dispersed water slug and electric field strength are discussed and explained in detail. Advantages and disadvantages of the suggested method, in comparison with existing capacitive noncontact methods, are also clarified. Unlike the noncontact methods of electric sensing, with the insulation dielectric layer over the electrodes, our electrodes are in a direct contact with the carrier phase. The results show that the method is promising for process applications and will be further improved. (paper)

  14. Electrical field of electrical appliances versus distance: A preliminary analysis

    Every household electrical appliance that is plugged in emits electric field even if it is not operating. The source where the appliance is plugged into and the components of household electrical appliance contribute to electric field emission. The electric field may cause unknown disturbance to the environment or also affect the human health and the effect might depends on the strength of the electric field emitted by the appliance. This paper will investigate the strength of the electric field emitted by four different electrical appliances using spectrum analyser. The strength will be captured at three different distances; (i) 1m (ii) 2m and (iii) 3m and analysis of the strength of the electrical field is done based on the three different distances. The measurement results show that the strength of the electric field is strongest when it is captured at 1m and the weakest at 3m from the electrical appliance. The results proved that the farther an object is located from the electrical appliance; the less effect the magnetic field has.

  15. Electric Field Effect in Intrinsic Josephson Junctions

    Koyama, T.

    The electric field effect in intrinsic Josephson junction stacks (IJJ's) is investigated on the basis of the capacitively-coupled IJJ model. We clarify the current-voltage characteristics of the IJJ's in the presence of an external electric field. It is predicted that the IJJ's show a dynamical transition to the voltage state as the external electric field is increased.

  16. Cell separation using electric fields

    Mangano, Joseph (Inventor); Eppich, Henry (Inventor)

    2009-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  17. Storing the Electric Energy Produced by an AC Generator

    Carvalho, P. Simeao; Lima, Ana Paula; Carvalho, Pedro Simeao

    2010-01-01

    Producing energy from renewable energy sources is nowadays a priority in our society. In many cases this energy comes as electric energy, and when we think about electric energy generators, one major issue is how we can store that energy. In this paper we discuss how this can be done and give some ideas for applications that can serve as a…

  18. Experimental Study on Electrical Characteristics of Advanced Unipolar Power Electronics Devices for High Current Operation of AC/DC Converter

    Large capacity power supply is required for energizing the magnetic field coil system of nuclear fusion experimental machine in future, and high efficiency and low operational loss of such power supply are important issues. Especially, for high current operation of large capacity power supply, the switching power electronics device of AC/DC converter for power supply should be more efficient and have lower on-state resistance than conventional one. Recently, some advanced power electronics devices have been developed, which are unipolar power device based on crystallized SiC material or super junction type modified unipolar power device based on crystallized Si material. Concerning the efficiency improvement of AC/DC converter, the temperature dependence of electrical characteristics of switching device is the key issue on operational loss reduction. On-state resistance and allowable operational temperature of switching device are directly related to the operational loss of AC/DC converter. The former one is the main parameter of conductive loss, which is dominant one of the operational loss of high current AC/DC converter, and it is effective to reduce the conductive loss for efficiency improvement. The latter one is related to the cooling capability of cooling equipment, which is a main auxiliary component of large capacity AC/DC converter. The temperature dependence of on-state resistance of SiC-based or Si-based advanced unipolar power electronics device will be expected to reduce the conductive loss and to simplify the cooling equipment of AC/DC converter. The allowable operational temperature of SiC power device is higher than that of Si power device, therefore it is also expected to minimize the cooling capability. Such electrical characteristics of SiC-based or Si-based advanced unipolar power electronics device will contribute to reduce the operational loss and to improve the operational efficiency of AC/DC converter. With the experimental results of

  19. Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-07-01

    The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ≪ v or ωτ ≪ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ≪ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

  20. Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

    Papathanassiou, Anthony N.; Mykhailiv, Olena; Echegoyen, Luis; Sakellis, Ilias; Plonska-Brzezinska, Marta E.

    2016-07-01

    The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

  1. Rydberg atoms in magnetic and electric fields

    This chapter examines highly excited atoms in the presence of a uniform field, magnetic or electric. It discusses Rydberg atoms in magnetic fields; Rydberg atoms in electric fields; and Rydberg atoms in crossed fields. It reviews present knowledge of this subject which is of great theoretical interest and which has recently benefited from laser spectroscopy

  2. Rapid magnetic microfluidic mixer utilizing AC electromagnetic field.

    Wen, Chih-Yung; Yeh, Cheng-Peng; Tsai, Chien-Hsiung; Fu, Lung-Ming

    2009-12-01

    This paper presents a novel simple micromixer based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). The micromixer chip is built using standard microfabrication and simple soft lithography, and the design can be incorporated as a subsystem into any chemical microreactor or a miniaturized biological sensor. An electromagnet driven by an AC power source is used to induce transient interactive flows between a ferrofluid and Rhodamine B. The alternative magnetic field causes the ferrofluid to expand significantly and uniformly toward Rhodamine B, associated with a great number of extremely fine fingering structures on the interface in the upstream and downstream regions of the microchannel. These pronounced fingering patterns, which have not been observed by other active mixing methods utilizing only magnetic force, increase the mixing interfacial length dramatically. Along with the dominant diffusion effects occurring around the circumferential regions of the fine finger structures, the mixing efficiency increases significantly. The miscible fingering instabilities are observed and applied in the microfluidics for the first time. This work is carried with a view to developing functionalized ferrofluids that can be used as sensitive pathogen detectors and the present experimental results demonstrate that the proposed micromixer has excellent mixing capabilities. The mixing efficiency can be as high as 95% within 2.0 s and a distance of 3.0 mm from the inlet of the mixing channel, when the applied peak magnetic field is higher than 29.2 Oe and frequency ranges from 45 to 300 Hz. PMID:19921677

  3. Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current

    Feinberg, B.; Gould, Harvey

    2014-09-01

    A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.

  4. Modelling and computation of AC fields and losses in high temperature superconductors

    This thesis is concerned with the modelling and the computation of the AC losses and electromagnetic fields in high temperature superconducting tapes using an E - J characteristic diffusion model. The AC losses in high temperature superconductors are modelled as a highly non-linear diffusion process. An empirical expression for modelling effective resistivity of the tape is extracted from the Rhyner's model and then used in the build up of the diffusion model. Formulation in terms of electric field E is used extensively and comprehensive explanations of why this model is used are given. Using the E formulation three different models that describe three different cases of the problem are developed. To understand the physical and the numerical phenomena that occur when a superconducting tape carries an alternating current or is exposed to an external variable magnetic field a one-dimensional model has been developed first. Comprehensive details and results of the principle and formulation of the primary model are given. The solid basis created by the one-dimensional model and the necessity of the model to be closer to the real tape drive us to two more realistic models, one where a silver layer is added on the top of the superconducting core, and the second one is the two-dimensional model where the edge effects and importance of non-linearity is emphasised. For both of these models comprehensive formulations and results are given. A collection of programs that solves the models has been created and tested, and the results obtained where successfully compared with results obtained by other authors through numerical and experimental means. The research demonstrates that the models developed are useful in exploring the mechanism of AC losses in superconducting tapes, the numerical programs allow prediction of losses under particular conditions and the applicability of different models (one and two-dimensional, the ''sandwich model'' and the critical state model

  5. Electric fields effect on liftoff and blowoff of nonpremixed laminar jet flames in a coflow

    Kim, Minkuk

    2010-01-01

    The stabilization characteristics of liftoff and blowoff in nonpremixed laminar jet flames in a coflow have been investigated experimentally for propane fuel by applying AC and DC electric fields to the fuel nozzle with a single-electrode configuration. The liftoff and blowoff velocities have been measured by varying the applied voltage and frequency of AC and the voltage and the polarity of DC. The result showed that the AC electric fields extended the stabilization regime of nozzle-attached flame in terms of jet velocity. As the applied AC voltage increased, the nozzle-attached flame was maintained even over the blowout velocity without having electric fields. In such a case, a blowoff occurred directly without experiencing a lifted flame. While for the DC cases, the influence on liftoff was minimal. There existed three different regimes depending on the applied AC voltage. In the low voltage regime, the nozzle-detachment velocity of either liftoff or blowoff increased linearly with the applied voltage, while nonlinearly with the AC frequency. In the intermediate voltage regime, the detachment velocity decreased with the applied voltage and reasonably independent of the AC frequency. At the high voltage regime, the detachment was significantly influenced by the generation of discharges. © 2009 The Combustion Institute.

  6. Computer Aided Mass Balance Analysis for AC Electric Arc Furnace Steelmaking

    (ü)nal Camdali; Murat Tunc

    2005-01-01

    A mass balance analysis was undertaken for liquid steel production using a computer program specially developed for the AC electric arc furnace at an important alloy steel producer in Turkey. The data obtained by using the computer program were found to be very close to the actual production ones.

  7. Electric double layer of anisotropic dielectric colloids under electric fields

    Han, M.; Wu, H.; Luijten, E.

    2016-07-01

    Anisotropic colloidal particles constitute an important class of building blocks for self-assembly directed by electrical fields. The aggregation of these building blocks is driven by induced dipole moments, which arise from an interplay between dielectric effects and the electric double layer. For particles that are anisotropic in shape, charge distribution, and dielectric properties, calculation of the electric double layer requires coupling of the ionic dynamics to a Poisson solver. We apply recently proposed methods to solve this problem for experimentally employed colloids in static and time-dependent electric fields. This allows us to predict the effects of field strength and frequency on the colloidal properties.

  8. Laser Assisted Electric Field Monitoring in a Cryogenic Environment

    Broering, Mark; Abney, Josh; Swank, Christopher; Filippone, Brad; Yao, Weijun; Korsch, Wolfgang; SNS-nEDM Collaboration

    2016-03-01

    The neutron EDM collaboration at the Spallation Neutron Source (ORNL) is using ultra-cold neutrons in liquid helium to improve the nEDM limit by two orders of magnitude. These neutrons will be stored in target cells located in a strong, stable electric field. Local radiation will generate charged particles which build up on the target cell walls reducing field strength and stability. The field fluctuations need to be kept below 1%, making it necessary to study this cell charging behavior, determine its effect on the experiment and find ways to mitigate this. A more compact test setup was designed to study this effect using smaller electrodes and cell. Charged particles are generated by ionizing the helium with a 137Cs source and the electric field is monitored via the electro-optic Kerr effect. Linearly polarized light is passed through the helium. The Kerr effect then introduces an ellipticity to the polarization that is proportional to the electric field squared. This allows an effective means of field monitoring. Nitrogen has a much stronger response to electric fields. This makes liquid nitrogen an ideal candidate for first tests. First results on the liquid nitrogen tests will be presented. This research is supported by DOE Grants: DE-FG02-99ER41101, DE-AC05-00OR22725.

  9. Discharge-generated electrical fields and electrical tree structures

    L. A. Dissado; Fothergill, J; Bromley, K. S.

    1998-01-01

    The discharge-avalanche (D-A) model for electrical tree propagation in polymers is founded entirely upon basic physical concepts. Electrical discharges in an existing tree structure are taken to raise the electrical field in the polymer both along the discharge path and particularly at the tree tips. As a result of the field increase, electron multiplication avalanches occur within the polymer causing damage, possibly through ionisation of polymer molecules, which is accumulated over a period...

  10. E-field dependence of the ac Stark effect probed by a bichromatic laser field

    In this paper we demonstrate, through numerical calculations, the possibility of determining the field dependence of the ac Stark effect through the interaction of an atom (or molecule) with a bichromatic ultrafast laser field. The time-dependent Schroedinger equation is solved for a single active electron confined to move in a square-well potential distorted by an intense Stark field in combination with a perturbative probe field which connects a pair of levels through photon absorption. The aim is to determine the field parameters that allow the dependence of the dynamic shift of the optically connected levels on the Stark field to be mapped out in real time. The calculations show that this can be achieved when the duration of the probe field is at least as short as the half-cycle period of the Stark field. An experimental realization of the proposed measurement scheme and its limitations are discussed. It is also possible, in principle, to adopt the ac Stark effect to determine the absolute phase of the carrier wave of an ultrafast laser pulse. (author)

  11. Absorption and Attenuation Coefficients Using the WET Labs ac-s in the Mid-Atlantic Bight: Field Measurements and Data Analysis

    Ohi, Nobuaki; Makinen, Carla P.; Mitchell, Richard; Moisan, Tiffany A.

    2008-01-01

    Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c (lambda) and a (lambda) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.

  12. Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

    Peak, S. C.

    1982-01-01

    An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

  13. Spin-current induced electric field

    Sun, QF; Guo, H; Wang, J

    2003-01-01

    We theoretically investigate properties of the induced electric field of a steady-state spin-current without charge current, using an 'equivalent magnetic charge' method. Several general formula for the induced electric field are derived which play the role of 'Biot-Savart law' and 'Ampere's law.' Conversely, a moving spin is affected by an external electric field and we derive an expression for the interaction torque.

  14. Entanglement generation by electric field background

    Ebadi, Zahra, E-mail: z.ebadi@ph.iut.ac.ir; Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir

    2014-12-15

    The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fermionic modes with respect to different parameters.

  15. Motional Spin Relaxation in Large Electric Fields

    Schmid, Riccardo; Plaster, B; Filippone, B.W.

    2008-01-01

    We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}$He atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}$He samples. The spin relaxation times $T_{1}$ (long...

  16. Quantification of high latitude electric field variability

    Crowley, G.; Hackert, C.L.

    2001-01-01

    Variability in the high latitude electric field has been identified as a major contributor to global Joule heating. Electric field patterns from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure are used to characterize the E-field temporal variability over the course of 18 hours. The standard deviation of the E-field magnitude on May 4, 1998 often exceeds the average value of the E-field magnitude. A significant fraction of this variability arises from oscillations wit...

  17. Effect of Electric Field on Outwardly Propagating Spherical Flame

    Mannaa, Ossama

    2012-06-01

    The thesis comprises effects of electric fields on a fundamental study of spheri­cal premixed flame propagation.Outwardly-propagating spherical laminar premixed flames have been investigated in a constant volume combustion vessel by applying au uni-directional electric potential.Direct photography and schlieren techniques have been adopted and captured images were analyzed through image processing. Unstretched laminar burning velocities under the influence of electric fields and their associated Markstein length scales have been determined from outwardly prop­agating spherical flame at a constant pressure. Methane and propane fuels have been tested to assess the effect of electric fields on the differential diffusion of the two fuels.The effects of varying equivalence ratios and applied voltages have been in­vestigated, while the frequency of AC was fixed at 1 KHz. Directional propagating characteristics were analyzed to identify the electric filed effect. The flame morphology varied appreciably under the influence of electric fields which in turn affected the burning rate of mixtures.The flame front was found to propagate much faster toward to the electrode at which the electric fields were supplied while the flame speeds in the other direction were minimally influenced. When the voltage was above 7 KV the combustion is markedly enhanced in the downward direction since intense turbulence is generated and as a result the mixing process or rather the heat and mass transfer within the flame front will be enhanced.The com­bustion pressure for the cases with electric fields increased rapidly during the initial stage of combustion and was relatively higher since the flame front was lengthened in the downward direction.

  18. Rotational diffusion model of orientational enhancement in AC field biased photorefractive polymers

    Pedersen, T.G.; Jespersen, K.G.; Johansen, P.M.

    2001-01-01

    The response of photorefractive (PR) polymers subject to AC field biasing is analyzed within the space-charge field formalism. The frequency dependence of orientational enhancement is taken into account using a rotational diffusion model for the angular distribution of chromophores. The possibili...... for simultaneous utilization of AC and orientational enhancement techniques in polymers is discussed for different values of the rotational diffusion time.......The response of photorefractive (PR) polymers subject to AC field biasing is analyzed within the space-charge field formalism. The frequency dependence of orientational enhancement is taken into account using a rotational diffusion model for the angular distribution of chromophores. The possibility...

  19. Sensorless AC electric motor control robust advanced design techniques and applications

    Glumineau, Alain

    2015-01-01

    This monograph shows the reader how to avoid the burdens of sensor cost, reduced internal physical space, and system complexity in the control of AC motors. Many applications fields—electric vehicles, wind- and wave-energy converters and robotics, among them—will benefit. Sensorless AC Electric Motor Control describes the elimination of physical sensors and their replacement with observers, i.e., software sensors. Robustness is introduced to overcome problems associated with the unavoidable imperfection of knowledge of machine parameters—resistance, inertia, and so on—encountered in real systems. The details of a large number of speed- and/or position-sensorless ideas for different types of permanent-magnet synchronous motors and induction motors are presented along with several novel observer designs for electrical machines. Control strategies are developed using high-order, sliding-mode and quasi-continuous-sliding-mode techniques and two types of observer–controller schemes based on backstepping ...

  20. An improved FEM model for computing transport AC loss in coils made of RABiTS YBCO coated conductors for electric machines

    AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors investigate the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in superconducting coils made from YBCO coated conductors for use in an all-superconducting electric machine. This paper presents an improved 2D finite element model for the cross-section of such coils, based on the H formulation. The model is used to calculate the transport AC loss of a racetrack-shaped coil using constant and magnetic field-dependent critical current densities, and the inclusion and exclusion of a magnetic substrate, as found in RABiTS (rolling-assisted biaxially textured substrate) YBCO coated conductors. The coil model is based on the superconducting stator coils used in the University of Cambridge EPEC Superconductivity Group's all-superconducting permanent magnet synchronous motor design. To validate the modeling results, the transport AC loss of a stator coil is measured using an electrical method based on inductive compensation by means of a variable mutual inductance. Finally, the implications of the findings on the performance of the motor are discussed.

  1. An improved FEM model for computing transport AC loss in coils made of RABiTS YBCO coated conductors for electric machines

    Ainslie, Mark D; Yuan Weijia; Flack, Timothy J; Coombs, Timothy A [Department of Engineering, University of Cambridge, 9 J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Rodriguez-Zermeno, Victor M [Department of Mathematics, Technical University of Denmark, Kongens Lyngby 2800 (Denmark); Hong Zhiyong, E-mail: mda36@cam.ac.uk [School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China)

    2011-04-15

    AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors investigate the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in superconducting coils made from YBCO coated conductors for use in an all-superconducting electric machine. This paper presents an improved 2D finite element model for the cross-section of such coils, based on the H formulation. The model is used to calculate the transport AC loss of a racetrack-shaped coil using constant and magnetic field-dependent critical current densities, and the inclusion and exclusion of a magnetic substrate, as found in RABiTS (rolling-assisted biaxially textured substrate) YBCO coated conductors. The coil model is based on the superconducting stator coils used in the University of Cambridge EPEC Superconductivity Group's all-superconducting permanent magnet synchronous motor design. To validate the modeling results, the transport AC loss of a stator coil is measured using an electrical method based on inductive compensation by means of a variable mutual inductance. Finally, the implications of the findings on the performance of the motor are discussed.

  2. Hall-Effect Based Semi-Fast AC On-Board Charging Equipment for Electric Vehicles

    Eva González-Romera; Enrique Romero-Cadaval; Javier Gallardo-Lozano; María Isabel Milanés-Montero

    2011-01-01

    The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-gri...

  3. High-Resolution ac Measurements of the Hall Effect in Organic Field-Effect Transistors

    Chen, Y.; Yi, H. T.; Podzorov, V.

    2016-03-01

    We describe a high resolving power technique for Hall-effect measurements, efficient in determining Hall mobility and carrier density in organic field-effect transistors and other low-mobility systems. We utilize a small low-frequency ac magnetic field (BrmsHall voltage, with the necessary corrections for Faraday induction. This method significantly enhances the signal-to-noise ratio and eliminates the necessity of using high magnetic fields in Hall-effect studies. With the help of this method, we are able to obtain the Hall mobility and carrier density in organic transistors with a mobility as low as μ ˜0.3 cm2 V-1 s-1 by using a compact desktop apparatus and low magnetic fields. We find a good agreement between Hall-effect and electric-field-effect measurements, indicating that, contrary to the common belief, certain organic semiconductors with mobilities below 1 cm2 V-1 s-1 can still exhibit a fully developed, band-semiconductor-like Hall effect, with the Hall mobility and carrier density matching those obtained in longitudinal transistor measurements. This suggests that, even when μ Hall-effect studies in a wide range of low-mobility materials and devices, where it is typically very difficult to resolve the Hall effect even in very high dc magnetic fields.

  4. Flux avalanches triggered by AC magnetic fields in superconducting thin films

    Flux avalanches are known to occur as a consequence of thermomagnetic instabilities. Some of their fingerprints are jumps in magnetization curves, or a paramagnetic reentrance in AC susceptibility measurements. In this work we have studied flux avalanches triggered by an AC field cycle by means of AC susceptibility and residual magnetization after an applied AC field measured as a function of an AC excitation field (h). These measurements allow comparing both results with magneto-optical imaging carried out in similar conditions. The results show a correspondence for the onset of the avalanche activity, as well as between the residual magnetic moment and the mean gray value calculated from the magneto-optical images in the remanent state.

  5. Positrons trapped in polyethylene: Electric field effect

    The intensity of the iot2-component of positrons annihilated in polyethylene is found to increase with increasing electric field, while the formation probability of the positron state responsible for this component remains independent of the field. (orig.) 891 HPOE

  6. Radial electric fields for improved tokamak performance

    The influence of externally-imposed radial electric fields on the fusion energy output, energy multiplication, and alpha-particle ash build-up in a TFTR-sized, fusing tokamak plasma is explored. In an idealized tokamak plasma, an externally-imposed radial electric field leads to plasma rotation, but no charge current flows across the magnetic fields. However, a realistically-low neutral density profile generates a non-zero cross-field conductivity and the species dependence of this conductivity allows the electric field to selectively alter radial particle transport

  7. Rotating artificial gauge magnetic and electric fields

    Lembessis, V E; Alshamari, S; Siddig, A; Aldossary, O M

    2016-01-01

    We consider the creation of artificial gauge magnetic and electric fields created when a two-level atom interacts with an optical Ferris wheel light field.These fields have the spatial structure of the optical Ferris wheel field intensity profile. If this optical field pattern is made to rotate in space then we have the creation of artificial electromagnetic fields which propagate in closed paths. The properties of such fields are presented and discussed

  8. Production Of Multi-magnetron Plasma By Using Polyphase Ac Glow Discharge In An Improved Multi-pole Magnetic Field

    Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro

    1998-10-01

    Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.

  9. Improved SCR ac Motor Controller for Battery Powered Urban Electric Vehicles

    Latos, T. S.

    1982-01-01

    An improved ac motor controller, which when coupled to a standard ac induction motor and a dc propulsion battery would provide a complete electric vehicle power train with the exception of the mechanical transmission and drive wheels was designed. In such a system, the motor controller converts the dc electrical power available at the battery terminals to ac electrical power for the induction motor in response to the drivers commands. The performance requirements of a hypothetical electric vehicle with an upper weight bound of 1590 kg (3500 lb) were used to determine the power rating of the controller. Vehicle acceleration capability, top speed, and gradeability requisites were contained in the Society of Automotive Engineers (SAE) Schedule 227a(d) driving cycle. The important capabilities contained in this driving cycle are a vehicle acceleration requirement of 0 to 72.4 kmph (0 to 45 mph) in 28 seconds a top speed of 88.5 kmph (55 mph), and the ability to negotiate a 10% grade at 48 kmph (30 mph). A 10% grade is defined as one foot of vertical rise per 10 feet of horizontal distance.

  10. Pulsed electric field inactivation in a microreactor

    Fox, M.B.

    2006-01-01

    Pulsed electric fields (PEF) is a novel, non-thermal pasteurization method which uses short, high electric field pulses to inactivate microorganisms. The advantage of a pasteurization method like PEF compared to regular heat pasteurization is that the taste, flavour, texture and nutritional value ar

  11. Substorm electric fields at nightside low latitude

    Hashimoto, K. K.; Kikuchi, T.; Tomizawa, I.; Nagatsuma, T.

    2014-12-01

    The convection electric field penetrates from the polar ionosphere to low latitude and drives the DP2 currents in the global ionosphere with an intensified equatorial electrojet (EEJ). The electric field often reverses its direction, that is, the overshielding occurs and causes the equatorial counterelectrojet (CEJ) during storm and substorms. In this paper we report that the overshielding electric field is detected by the HF Doppler sounders at low latitude on the nightside. We analyzed the Doppler frequency of the HF radio signals propagated over 120 km in Japan at frequencies of 5 and 8 MHz and compared with the equatorial EEJ/CEJ during the substorm expansion phase. We found that the overshielding electric field reaches around 2 mV/m during major substorms (AL <-1800 nT). Taking the geometrical attenuation into account, we estimate the equatorial electric field to be about 1.5 mV/m. We also found that the correlation coefficient was 0.94 between the overshielding electric field and eastward equatorial electrojet at YAP on the night side. The electric field drives the eastward electrojets in the equatorial ionosphere on the night side. It is to be noted that the overshielding electric field is observed on the nightside at low latitude during the major substorms, while the convection electric field is dominant during smaller size substorms, as the CEJ flows on the dayside. These results suggest that the overshielding electric field associated with the Region-2 field-aligned currents becomes dominant during substorms at low latitude on the nightside as well as on the dayside.

  12. Classical theory of electric and magnetic fields

    Good, Roland H

    1971-01-01

    Classical Theory of Electric and Magnetic Fields is a textbook on the principles of electricity and magnetism. This book discusses mathematical techniques, calculations, with examples of physical reasoning, that are generally applied in theoretical physics. This text reviews the classical theory of electric and magnetic fields, Maxwell's Equations, Lorentz Force, and Faraday's Law of Induction. The book also focuses on electrostatics and the general methods for solving electrostatic problems concerning images, inversion, complex variable, or separation of variables. The text also explains ma

  13. Influence of 50Hz electric field generated by AC high-voltage overhead power lines on human body%高压交流架空线路工频电场对人体的影响

    王杰; 张小青; 王涛; 陈灏; 盛财旺; 刘峰

    2011-01-01

    This paper is mainly aimed at discussing the calculation method of human-earth induced voltage which is generated by AC high-voltage overhead power lines, as well as touch-current of human body. At the beginning of this paper, the human body is simply equivalent to a cylinder, and the calculation model of human-earth induced voltage generated by single phase high-voltage overhead power line is derived by Equivalent Charge Method. On basis of it, this model and calculation method are further extended to the three-phase high-voltage overhead power lines situation. Secondly, this paper applies the derived model and calculation method to calculate the current through the human body when the human body touches the conductor under overhead power lines. It has the advantages of simple calculation procedure, small calculation burden, and convenient to engineering application.%本文主要讨论了高压交流架空线路下人体对地感应电位和人体接触电流的算法.文中首先把人体简化等效为一个等值圆柱,用等效电荷法导出了单相架空线路下人体对地电位的计算模型.在此基础上,进一步将模型与算法推广到三相高压交流架空线路的情况.然后本文运用所推出的模型与算法计算出人接触架空线路下的导体时通过人体的电流.本文推出的模型与算法具有计算步骤简单,计算量小,便于工程运用等优势.

  14. The convection electric field in auroral substorms

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2001-01-01

    Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained...... this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within...... the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection...

  15. Generation of DC electric fields due to vortex rectification in superconducting films

    The introduction of the manuscript reviews different mechanisms of generation of permanent electric fields by AC driven vortex lattices in type-II superconductors due to artificial symmetry breaking. The second part shows that superconducting Pb and Nb films (strips or crosses) with or without symmetric periodic pinning centers, subject to a magnetic field perpendicular to the film plane, also exhibit magnetically tunable AC current rectification. At low drive frequencies, not far below the critical temperature, the superconducting films work as one-dimensional rectifiers (i.e. generate an uniform DC electric field along the direction of the AC current) due to unavoidable small vortex pinning asymmetry. At higher frequencies, above 105 Hz, rectification gradually becomes two-dimensional with a strongly non-uniform generated DC electric field. DC voltages, either longitudinal or transversal to the AC current are tunable with the applied magnetic field. The rectified voltage depends strongly on the temperature and the AC drive intensity. In superconductors with periodic pinning centers the rectified voltage varies periodically with the number of vortices per pinning center. Not far below T c, the generated DC electric field is nearly opposite on the opposite film sides. The unusual two-dimensional character of rectification at high frequencies close to T c could be qualitatively understood in terms of local rectification due the oppositely directed asymmetric edge barriers (Bean-Livingston type) or by slowly relaxing electric fields generated by local critical current excess. Anisotropic pinning effects represent a dominant contribution to the rectification further below T c. Since in experiments on rectification in superconductors this electric field adds to the one due to, e.g., anisotropic vortex pinning, one has to take into account its presence when interpreting the rectification experiments

  16. Electric field generation in martian dust devils

    Barth, Erika L.; Farrell, William M.; Rafkin, Scot C. R.

    2016-04-01

    Terrestrial dust devils are known to generate electric fields from the vertical separation of charged dust particles. The particles present within the dust devils on Mars may also be subject to similar charging processes and so likely contribute to electric field generation there as well. However, to date, no Mars in situ instrumentation has been deployed to measure electric field strength. In order to explore the electric environment of dust devils on Mars, the triboelectric dust charging physics from the Macroscopic Triboelectric Simulation (MTS) code has been coupled to the Mars Regional Atmospheric Modeling System (MRAMS). Using this model, we examine how macroscopic electric fields are generated within martian dust disturbances and attempt to quantify the time evolution of the electrodynamical system. Electric fields peak for several minutes within the dust devil simulations. The magnitude of the electric field is a strong function of the size of the particles present, the average charge on the particles and the number of particles lifted. Varying these parameters results in peak electric fields between tens of millivolts per meter and tens of kilovolts per meter.

  17. Characteristics of the magnetic field under hybrid ac/dc high voltage transmission lines

    In recent years, the possibility for ac and dc transmission lines running parallel to each other, sharing the same right-of-way (ROW) or even the same-tower has increased. Design of such hybrid ac/dc networks requires a precise calculation of the magnetic field around and under them. This paper presents quantitative analysis of the magnetic field at 1-m height above ground surface for different hybrid ac/dc transmission lines. Lateral profiles for typical 275, 132 (running in Kuwait), 500, 220 and 132 kV (running in Egypt) ac transmission lines after adding bipolar dc lines are presented. The magnetic vector potential concept, as extended to multi-conductor transmission lines employing the superposition principle is used to model and calculate the RMS values of the magnetic field generated by the hybrid ac/dc lines at any point in the space. The RMS values of the field are determined directly without dividing the ac supply cycle into a sufficient number of subintervals. The presented graphs are useful for setting the maximum allowable ac and dc line current magnitudes, for existing lines, corresponding to a certain safe level of the magnetic field at the edge of right-of-way. (author)

  18. Magneto-Induced ac Electrical Permittivity of Metal-Dielectric Composites with a Two Characteristic Length Scales Periodic Microstructure

    A new effect was recently predicted in conducting composites that have a periodic microstructure: an induced strongly anisotropic dc magneto-resistance. This phenomenon is already verified on high mobility n-GaAs films. Here we discuss the possibility of observing analogous behavior in the ac electric permittivity of a metal-dielectric composite with a periodic microstructure in the presence of a strong magnetic field. We developed new analytical and numerical methods to treat the low-frequency magneto-optical properties in composite media with both disordered and periodic conducting micro-structures. Those methods allow us to study composites with inclusions of arbitrary shape (and arbitrary volume fraction) at arbitrarily strong magnetic field. This is exploited in order to calculate an effective dielectric tensor for this system as a function of applied magnetic field and ac frequency. We show that in a non-dilute metal-dielectric composite medium the magneto-plasma resonance and the cyclotron resonance depend upon both the applied magnetic field as well as on the geometric shape of the inclusion. Near such a resonance, it is possible to achieve large values for the ratio of the off-diagonal-to-diagonal electric permittivity tensor components, εxy/εxx, (since εxx→0, while εxy≠0), which is analogous to similar ratio of the resistivity tensor components, ρxy/ρxx, in the case of dc magneto-transport problem. Motivated by this observation and by results of previous studies of dc magneto-transport in composite conductors, we then performed a numerical study of the ac magneto-electric properties of a particular metal-dielectric composite film with a periodic columnar microstructure which has a two characteristic length scales. The unit cell of such composite is prepared as follows: We placed the conducting square (in cross section) rods (first characteristic length scale) along the perimeter of the unit cell in order to create a dielectric host with large

  19. Electric Conductivity of Carbon Nanoparticles Stimulated by Electric Field

    Host-guest interactions can be the unique method of spin manipulation in nanoscale. Strong changes in spin localization are generated when potential barriers between nanographitic units of activated carbon fibers are modified by interaction with adsorbed molecules. Stronger modifications occur when dipolar guest molecules are stimulated with external electric field. We report experimental results which show the influence of electric field on the spin localization in activated carbon fibers. (authors)

  20. Electric Field Dependence of the Electrical Conductivity of VOx

    Garcia, N.

    1985-01-01

    We have observed non-ohmic behavior in the resistivity of VOx for very small electric fields. In an attempt to explain these results several models are considered. We suggest that the sharpening of the transition to the insulating state with applied electric field is due to a reduction of the length of time during which regions of the sample fluctuate into the insulating state.

  1. Recent Research Results in the Field of Electric Drives and Mechatronics

    Jan Vittek; Velaria Hrabovcova; Rastislav Tabacek

    2003-01-01

    The paper presents an overview of research results achieved in the field of Electrical Drives and Mechatronics for the period of three years. The achieved outputs are formed into three individual parts. In the field of Electric Drives the most significant outputs have been achieved in the development of a new control algorithms for a.c. drives under general name 'Forced Dynamics Control' , in improvement of shaft sensorless control methods and in implementation of developed algorithms via dig...

  2. Delocalization of Phase Perturbations and the Stability of AC Electricity Grids

    Kettemann, S.

    2015-01-01

    The energy transition towards an increased supply of renewable energy raises concerns that existing electricity grids, built to connect few centralized large power plants with consumers, may become more difficult to control and stabilized with a rising number of decentralized small scale generators. Here, we aim to study therefore, how local phase perturbations which may be caused by local power fluctuations, affect the AC grid stability. To this end, we start from nonlinear power balance equ...

  3. Local electric field measurements by optical tweezers

    G. Pesce

    2011-09-01

    Full Text Available We report a new technique to measure direction and amplitude of electric fields generated by microelectrodes embedded in polar liquid environment, as often used in microfluidic devices. The method is based on optical tweezers which act as sensitive force transducer while a trapped charged microsphere behaves as a probe. When an electric field is applied the particles moves from its equilibrium position and finishes in a new equilibrium position where electric and optical forces are balanced. A trapped bead is moved to explore the electric field in a wide region around the microelectrodes. In such way maps of electric fields with high spatial resolution can be reconstructed even for complex electrode geometries where numerical simulation approaches can fail. Experimental results are compared with calculations based on finite element analysis simulation.

  4. Electric field replaces gravity in laboratory

    Gorgolewski, S.

    For several years experiments in physical laboratories and in the fitotron have shown that one can replace gravitational field with electrical fields for plants. First obvious experiments in strong electrical fields in the MV/m regi on show that any materials and living plants respond immediately to Coulomb forces. Such fields are found in nature during thunderstorms. One has to be very careful in handling such strong fields for safety reasons. The fair weather global electrical field is about 20,000 times weaker. The coulomb forces are proportional to the square of the field strength and are thus 400 milion times weaker for a field of the order of 100 V/m.Yet it was found that some plants respond to such "weak" fields. We must remember that the electrical field is a factor of 10 38 times stronger than gravitational interaction. In plants we have dissociated in water mineral salts and the ions are subject to such ernormous forces. It was shown and published that the positive charges in the air in fields of the order of 3kV/m enhance lettuce growth by a factor of four relative to fields about 30 times weaker (100V/m). Reversal of the field polarity reverses the direction of plant growth and retards the plant's growth. Such fields overpower the gravitropism in the laboratory. More so horizontal electrical field is othogonal to gravity, now the fields do not see each other. Lettuce now growth horizontally ignoring the gravitational field. We can thus select the plants whose electrotropism even in the laboratory overwhelms gravity. This is important for the long space flights that we must grow vegetarian food for the crew. The successful harvesting of wheat in orbit does not contradict our experimental findings because wheat is not electrotropic like all plants from the grass family. The results of fitotron experiments with kV/m electrical fields are richly illustrated with colour digital photographs. We also subjected the candle flame to very strong horizontal

  5. Manipulation of nano-entities in suspension by electric fields

    Fan, Donglei

    Nanoscale entities, including nanospheres, nanodisks, nanorings, nanowires and nanotubes are potential building blocks for nanoscale devices. Among them, nanowires is an important type of nanoparticles, due to the potential application in microelectronics and bio-diagnosis. Manipulation of nanowires in suspension has been a formidable problem. As described in this thesis, using AC electric fields applied to strategically designed microelectrodes, nanowires in suspension can be driven to align, to chain, to accelerate in directions parallel and perpendicular to its orientation, to concentrate onto designated places, and to disperse in a controlled manner with high efficiency despite an extremely low Reynolds number at the level of 10-5. Randomly oriented nanowires in suspension can be rapidly assembled into extended nonlinear structures within seconds. We show that both the electric field and its gradient play the essential roles of aligning and transporting the nanowires into scaffolds according to the electric field distributions inherent to the geometry of the microelectrodes. The assembling efficiency depends strongly on the frequency of the applied AC voltages and varies as square of the voltage. Furthermore, nanowires have been rotated by AC electric fields applied to strategically designed electrodes. The rotation of the nanowires can be instantly switched on or off with precisely controlled rotation speed (to at least 25000 rpm), definite chirality, and total angle of rotation. This new method has been used to controllably rotate magnetic and non-magnetic nanowires as well as multi-wall carbon nanotubes. We have also produced a micromotor using a rotating nanowire that can drive particles into circular motion. This has application to microfluidic devices, micro-stirrers, and micro electromechanical systems (MEMS). To move and place nanowires onto designated locations with high precision, electrophoretic force has been combined with dielectrophoretic force to

  6. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids

  7. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Rajnak, Michal; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj; Kopcansky, Peter; Timko, Milan

    2015-08-01

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  8. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Rajnak, Michal; Kopcansky, Peter; Timko, Milan [Institute of Experimental Physics SAS, Watsonova 47, 04001 Košice (Slovakia); Petrenko, Viktor I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Avdeev, Mikhail V. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Ivankov, Olexandr I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Moscow Institute of Physics and Technology, Institutskiy per. 9, Dolgoprudniy 141700 (Russian Federation); Feoktystov, Artem [Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching (Germany); Dolnik, Bystrik; Kurimsky, Juraj [Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice (Slovakia)

    2015-08-17

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  9. ESTIMATING ELECTRIC FIELDS FROM VECTOR MAGNETOGRAM SEQUENCES

    Determining the electric field distribution on the Sun's photosphere is essential for quantitative studies of how energy flows from the Sun's photosphere, through the corona, and into the heliosphere. This electric field also provides valuable input for data-driven models of the solar atmosphere and the Sun-Earth system. We show how observed vector magnetogram time series can be used to estimate the photospheric electric field. Our method uses a 'poloidal-toroidal decomposition' (PTD) of the time derivative of the vector magnetic field. These solutions provide an electric field whose curl obeys all three components of Faraday's Law. The PTD solutions are not unique; the gradient of a scalar potential can be added to the PTD electric field without affecting consistency with Faraday's Law. We then present an iterative technique to determine a potential function consistent with ideal MHD evolution; but this field is also not a unique solution to Faraday's Law. Finally, we explore a variational approach that minimizes an energy functional to determine a unique electric field, a generalization of Longcope's 'Minimum Energy Fit'. The PTD technique, the iterative technique, and the variational technique are used to estimate electric fields from a pair of synthetic vector magnetograms taken from an MHD simulation; and these fields are compared with the simulation's known electric fields. The PTD and iteration techniques compare favorably to results from existing velocity inversion techniques. These three techniques are then applied to a pair of vector magnetograms of solar active region NOAA AR8210, to demonstrate the methods with real data. Careful examination of the results from all three methods indicates that evolution of the magnetic vector by itself does not provide enough information to determine the true electric field in the photosphere. Either more information from other measurements, or physical constraints other than those considered here are necessary to find

  10. Computer simulations of single particles in external electric fields.

    Zhou, Jiajia; Schmid, Friederike

    2015-09-14

    Applying electric fields is an attractive way to control and manipulate single particles or molecules, e.g., in lab-on-a-chip devices. However, the response of nanosize objects in electrolyte solution to external fields is far from trivial. It is the result of a variety of dynamical processes taking place in the ion cloud surrounding charged particles and in the bulk electrolyte, and it is governed by an intricate interplay of electrostatic and hydrodynamic interactions. Already systems composed of one single particle in electrolyte solution exhibit a complex dynamical behaviour. In this review, we discuss recent coarse-grained simulations that have been performed to obtain a molecular-level understanding of the dynamic and dielectric response of single particles and single macromolecules to external electric fields. We address both the response of charged particles to constant fields (DC fields), which can be characterized by an electrophoretic mobility, and the dielectric response of both uncharged and charged particles to alternating fields (AC fields), which is described by a complex polarizability. Furthermore, we give a brief survey of simulation algorithms and highlight some recent developments. PMID:26238433

  11. Electric-field Induced Microdynamics of Charged Rods

    Kyongok eKang

    2014-12-01

    Full Text Available Electric-field induced phase/state transitions are observed in AC electric fields with small amplitudes and low frequencies in suspensions of charged fibrous viruses (fd, which are model systems for highly charged rod-like colloids. Texture- and particle-dynamics in these field-induced states, and on crossing transition lines, are explored by image time-correlation and dynamic light scattering, respectively. At relatively low frequencies, starting from a system within the isotropic-nematic coexistence region, a transition from a nematic to a chiral nematic is observed, as well as a dynamical state where nematic domains melt and reform. These transitions are preliminary due to field-induced dissociation/association of condensed ions. At higher frequencies a uniform state is formed that is stabilized by hydrodynamic interactions through field-induced electro-osmotic flow where the rods align along the field direction. There is a point in the field-amplitude versus frequency plane where various transition lines meet. This point can be identified as a non-equilibrium critical point, in the sense that a length scale and a time scale diverge on approach of that point. The microscopic dynamics exhibits discontinuities on crossing transition lines that were identified independently by means of image and signal correlation spectroscopy.

  12. Nonlinear cell response to strong electric fields

    Bardos, D. C.; Thompson, C. J.; Yang, Y. S.; Joyner, K. H.

    2000-07-01

    The response of living cells to externally applied electric fields is of widespread interest. In particular, the intensification of electric fields across cell membranes is believed to be responsible, through membrane rupture and reversible membrane breakdown processes, for certain types of tissue damage in electrical trauma cases which cannot be attributed to Joule heating. Large elongated cells such as skeletal muscle fibres are particularly vulnerable to such damage. Previous theoretical studies of field intensification across cell membranes in such cells have assumed the membrane current to be linear in the applied field (Ohmic membrane conductivity) and were limited to sinusoidal applied fields. In this paper, we investigate a simple model of a long cylindrical cell, corresponding to nerve or skeletal muscle cells. Employing the electroquasistatic approximation, a system of coupled first-order differential equations for the membrane electric field is derived which incorporates arbitrary time dependence in the external field and nonlinear membrane response (non-Ohmic conductivity). The behaviour of this model is investigated for a variety of applied fields in both the linear and highly nonlinear regimes. We find that peak membrane fields predicted by the nonlinear model are approximately twice as intense, for low-frequency electrical trauma conditions, as those of the linear theory.

  13. Calorimetric method of ac loss measurement in a rotating magnetic field

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  14. Calorimetric method of ac loss measurement in a rotating magnetic field

    Ghoshal, P. K. [Oxford Instruments NanoScience, Abingdon, Oxfordshire OX13 5QX (United Kingdom); Coombs, T. A.; Campbell, A. M. [Department of Engineering, Electrical Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

    2010-07-15

    A method is described for calorimetric ac-loss measurements of high-T{sub c} superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  15. Calorimetric method of ac loss measurement in a rotating magnetic field

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  16. Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam.

    Ortendahl, T W; Högstedt, P; Odelius, H; Norén, J G

    1988-11-01

    Metallic taste has been reported from divers working with underwater electric welding and cutting. An in vitro model was designed to simulate the intraoral situation of the divers with respect to the magnetic field. Potentiostatic analyses were performed on amalgam samples exposed to AC and DC magnetic fields. Morphologic changes were analyzed using differential interference light microscopy and scanning electron microscopy. Chemical changes on the surface of the amalgam samples were analyzed with secondary ion mass spectrometry. Results demonstrated that dental amalgams exposed to a specific AC magnetic field underwent morphologic and chemical changes in the superficial amalgam layers. PMID:3227577

  17. Electropumping of water with rotating electric fields

    Hansen, Jesper Schmidt; De Luca, Sergio; Todd, Billy;

    2013-01-01

    exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum...

  18. Microfluidic Screening of Electric Fields for Electroporation

    Garcia, Paulo A.; Zhifei Ge; Jeffrey L. Moran; Buie, Cullen R

    2016-01-01

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced i...

  19. Dimensional crossover driven by an electric field.

    Aron, Camille; Kotliar, Gabriel; Weber, Cedric

    2012-02-24

    We study the steady-state dynamics of the Hubbard model driven out of equilibrium by a constant electric field and coupled to a dissipative heat bath. For a very strong field, we find a dimensional reduction: the system behaves as an equilibrium Hubbard model in lower dimensions. We derive steady-state equations for the dynamical mean-field theory in the presence of dissipation. We discuss how the electric field induced dimensional crossover affects the momentum resolved and integrated spectral functions, the energy distribution function, as well as the steady current in the nonlinear regime. PMID:22463546

  20. Achieving High Performance in AC-Field Driven Organic Light Sources

    Xu, Junwei; Carroll, David L.; Smith, Gregory M.; Dun, Chaochao; Cui, Yue

    2016-04-01

    Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional increases in device performance. To do this we replace the insulator layer in a typical field-activated organic light emitting device with a nanostructured, wide band gap semiconductor layer. This layer acts as a gate between the emitter layer and the voltage contact. Time resolved device characterization shows that, at high-frequencies (over 40 kHz), the semiconductor layer allows for charge accumulation in the forward bias, light generating part of the AC cycle and charge compensation in the negative, quiescent part of the AC cycle. Such gated AC organic devices can achieve a non-output coupled luminance of 25,900 cd/m2 with power efficiencies that exceed both the insulator-based AC devices and OLEDs using the same emitters. This work clearly demonstrates that by realizing balanced management of charge, AC-driven organic light emitting devices may well be able to rival today’s OLEDs in performance.

  1. Directed Orientation of Asymmetric Composite Dumbbells by Electric Field Induced Assembly

    Nagao, D.; Sugimoto, M.; Okada, A.; Ishii, H.; Konno, M.; Imhof, A.; van Blaaderen, A.

    2012-01-01

    Assembly and directed orientation of anisotropic particles with an external ac electric field in a range from 1 kHz to 2 MHz were studied for asymmetric composite dumbbells incorporating a silica, titania, or titania/silica (titania:silica = 75:25 vol %) sphere. The asymmetric composite dumbbells, w

  2. Rotating Capacitor Measures Steady Electric Fields

    Johnston, A. R.; Kirkham, H.; Eng, B.

    1986-01-01

    Portable sensor measures electric fields created by dc powerlines or other dc-high-voltage sources. Measures fields from 70 to 50,000 V/m with linearity of 2 percent. Sensor used at any height above ground. Measures both magnitude and direction of field and provides signals representing these measurements to remote readout device. Sensor functions with minimal disturbance of field it is measuring.

  3. Progress on advanced dc and ac induction drives for electric vehicles

    Schwartz, H. J.

    1982-01-01

    Progress is reported in the development of complete electric vehicle propulsion systems, and the results of tests on the Road Load Simulator of two such systems representative of advanced dc and ac drive technology are presented. One is the system used in the DOE's ETV-1 integrated test vehicle which consists of a shunt wound dc traction motor under microprocessor control using a transistorized controller. The motor drives the vehicle through a fixed ratio transmission. The second system uses an ac induction motor controlled by transistorized pulse width modulated inverter which drives through a two speed automatically shifted transmission. The inverter and transmission both operate under the control of a microprocessor. The characteristics of these systems are also compared with the propulsion system technology available in vehicles being manufactured at the inception of the DOE program and with an advanced, highly integrated propulsion system upon which technology development was recently initiated.

  4. Midday reversal of equatorial ionospheric electric field

    R. G. Rastogi

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  5. Nanoparticle Near-Surface Electric Field.

    Chkhartishvili, Levan

    2016-12-01

    Theoretical studies show that surface reconstruction in some crystals involves splitting the surface atomic layer into two-upper and lower-sublayers consisting of atoms with only positive or only negative effective electric charges, respectively. In a macroscopic crystal with an almost infinite surface, the electric field induced by such a surface-dipole is practically totally concentrated between the sublayers. However, when the material is powdered and its particles are of sufficiently small sizes, an electric field of a significant magnitude can be induced outside the sublayers as well. We have calculated the distribution of the electric field and its potential induced at the surface of a disc-shaped particle. The suggested novel nanoscale effect explains the increase in physical reactivity of nanopowders with decreasing particle sizes. PMID:26831686

  6. Achieving High Performance in AC-Field Driven Organic Light Sources

    Junwei Xu; David L. Carroll; Smith, Gregory M.; Chaochao Dun; Yue Cui

    2016-01-01

    Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional in...

  7. Magneto-optical measurements on high-temperature superconductors influenced by AC-fields

    In this work magneto-optical measurements on YBa2Cu3O7-x and MgB2 thin films were done. For YBCO the influence of AC-pulses on the flux and current density of a thin film with transport current was investigated. For MgB2 the influence of AC-fields on the homogenous and dendritic flux penetration was researched. (orig.)

  8. Rotationally Vibrating Electric-Field Mill

    Kirkham, Harold

    2008-01-01

    A proposed instrument for measuring a static electric field would be based partly on a conventional rotating-split-cylinder or rotating-split-sphere electric-field mill. However, the design of the proposed instrument would overcome the difficulty, encountered in conventional rotational field mills, of transferring measurement signals and power via either electrical or fiber-optic rotary couplings that must be aligned and installed in conjunction with rotary bearings. Instead of being made to rotate in one direction at a steady speed as in a conventional rotational field mill, a split-cylinder or split-sphere electrode assembly in the proposed instrument would be set into rotational vibration like that of a metronome. The rotational vibration, synchronized with appropriate rapid electronic switching of electrical connections between electric-current-measuring circuitry and the split-cylinder or split-sphere electrodes, would result in an electrical measurement effect equivalent to that of a conventional rotational field mill. A version of the proposed instrument is described.

  9. Electrohydrodynamic Displacement of Polarizable Liquid Interfaces in an Alternating Current Electric Field

    Gagnon, Zachary

    2015-11-01

    In this work, we investigate Maxwell-Wagner polarization at electrically polarizable liquid interfaces. An AC electric field is applied across a liquid electrical interface created between two co-flowing microfluidic fluid streams with different electrical properties. When potentials as low as 2 volts are applied, we observe a frequency dependent interfacial displacement that is dependent on the relative differences in the electrical conductivity and dielectric constant between the two liquids. At low frequency this deflection is dependent on electrical conductivity, and only depends on dielectric constant at high frequency. At intermediate frequencies, we observe a crossover that is independent of applied voltage, sensitive to both fluid electrical properties, and where no displacement is observed. An analytical polarization model is presented that predicts the liquid interfacial crossover frequency, the dependence of interfacial displacement on liquid electrical conductivity and dielectric constant, and accurately scales the interface displacement measurements. The results show that liquid interfaces are capable of polarizing under AC electric fields and being precisely deflected in a direction and magnitude that is dependent on the applied electric field frequency.

  10. Computer Simulation of Electric Field Lines.

    Kirkup, L.

    1985-01-01

    Describes a computer program which plots electric field line plots. Includes program listing, sample diagrams produced on a BBC model B microcomputer (which could be produced on other microcomputers by modifying the program), and a discussion of the properties of field lines. (JN)

  11. Electric field measurements from Halley, Antarctica

    Nicoll, Keri; Harrison, R. Giles

    2016-04-01

    Antarctica is a unique location for the study of atmospheric electricity. Not only is it one of the most pollutant free places on Earth, but its proximity to the south magnetic pole means that it is an ideal location to study the effects of solar variability on the atmospheric electric field. This is due to the reduced shielding effect of the geomagnetic field at the poles which leads to a greater flux of incoming Galactic Cosmic Rays (GCRs) as well as an increased probability of energetic particle precipitation from SEPs and relativistic electrons. To investigate such effects, two electric field mills of different design were installed at the British Antarctic Survey Halley base in February 2015 (75. 58 degrees south, 26.66 degrees west). Halley is situated on the Brunt Ice Shelf in the south east of the Weddell Sea and has snow cover all year round. Preliminary analysis has focused on selection of fair weather criteria using wind speed and visibility measurements which are vital to assess the effects of falling snow, blowing snow and freezing fog on the electric field measurements. When the effects of such adverse weather conditions are removed clear evidence of the characteristic Carnegie Curve diurnal cycle exists in the Halley electric field measurements (with a mean value of 50V/m and showing a 40% peak to peak variation in comparison to the 34% variation in the Carnegie data). Since the Carnegie Curve represents the variation in thunderstorm activity across the Earth, its presence in the Halley data confirms the presence of the global atmospheric electric circuit signal at Halley. The work presented here will discuss the details of the Halley electric field dataset, including the variability in the fair weather measurements, with a particular focus on magnetic field fluctuations.

  12. The effect of high frequency electric field on hypersound amplification in superlattice

    Propagation of hypersound in a semiconductor superlattice (SL) in the presence of an external electric field of the form E = E0 + E1 cosωt has been studied theoretically. The analytical expressions obtained for the absorption coefficient Γ are presented graphically. It is observed that in the absence of a.c. electric field the dependence of Γ on Eo is nonlinear unlike the homogeneous bulk material where the dependence of Γ on E0 is linear. The inclusion of a.c. electric field affects the elation Γ on E0 depending on the values of E1 and ωτ. For a given E1, the peaks of the curve Γ0 on E0 decrease, shift and eventually oscillate for increasing values of ωτ i.e. from ωτ much less than 1 to ωτ much greater than 1. (author). 19 refs, 6 figs

  13. Field Models in Electricity and Magnetism

    Barba, Paolo Di; Wiak, S

    2008-01-01

    Covering the development of field computation in the past forty years, Field Models in Electricity and Magnetism intends to be a concise, comprehensive and up-to-date introduction to field models in electricity and magnetism, ranging from basic theory to numerical applications. The approach assumed throughout the whole book is to solve field problems directly from partial differential equations in terms of vector quantities. Theoretical issues are illustrated by practical examples. In particular, a single example is solved by different methods so that, by comparison of results, limitations and advantages of the various methods are made clear. The subjects of the synthesis of fields and of the optimal design of devices, which are growing in research and so far have not been adequately covered in textbooks, are developed in addition to more classical subjects of analysis. Topics covered include: vector fields: electrostatics, magnetostatics, steady conduction; analytical methods for solving boundary-value probl...

  14. Pair production from an external electric field

    We solve numerically the problem of pair production from an external electric field in 1 + 1 dimensions including the quantum back-reaction from the produced pairs. We find that in the linear regime our numerical results agree perfectly with analytic calculations. In the strong field regime where tunnelling is uninhibited we determine the time it takes for the electric field to degrade due to energy transfer to the large number of pion field degrees of freedom. The problem has three time scales--the oscillation frequency of the charged quanta, the induced plasma oscillation frequency due to the production of pairs and finally the time scale for energy to be transferred from the electromagnetic field to the pion field. 4 refs., 5 figs

  15. Rotational diffusion model of orientational enhancement in AC field biased photorefractive polymers

    Pedersen, T.G.; Jespersen, K.G.; Johansen, P.M.

    2001-01-01

    The response of photorefractive (PR) polymers subject to AC field biasing is analyzed within the space-charge field formalism. The frequency dependence of orientational enhancement is taken into account using a rotational diffusion model for the angular distribution of chromophores. The possibility...

  16. Electric field profiles in obstructed helium discharge

    Fendel, Peter; Ganguly, Biswa; Bletzinger, Peter

    2014-10-01

    Axial and radial variations of electric field have been measured in dielectric shielded 25 mm diameter parallel plate electrode for 2 mA, 2250 V helium dc discharge at 1.75 Torr with 6.5 mm gap. The axial and radial electric field profiles have been measured from the polarization dependent Stark splitting of 21S --> 11 1P transition through collision induced fluorescence from 43D --> 23P. The electric field values showed a strong radial variation peaking up to 5 kV/cm near the cathode radial boundary, and decreasing to about 1 kV/cm near the anode, suggesting the formation of an obstructed discharge for this low Pd condition. Also, the on-axis electric field was nearly constant across the gap indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with COMSOL finite element modeling program. The model discharge dimensions were selected to match the experimental dimensions. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) =ρ0 (r/r0)3 , where ρ(r) is the local space charge density, ρ0 is the maximum space-charge density, r the local radial value and r0 the radius of the electrode.

  17. Nanoparticle Near-Surface Electric Field

    Chkhartishvili, Levan

    2016-01-01

    Theoretical studies show that surface reconstruction in some crystals involves splitting the surface atomic layer into two—upper and lower—sublayers consisting of atoms with only positive or only negative effective electric charges, respectively. In a macroscopic crystal with an almost infinite surface, the electric field induced by such a surface-dipole is practically totally concentrated between the sublayers. However, when the material is powdered and its particles are of sufficiently smal...

  18. Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field.

    Masashi Suzuki

    Full Text Available We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles.

  19. Microwave electric field sensing with Rydberg atoms

    Stack, Daniel T.; Kunz, Paul D.; Meyer, David H.; Solmeyer, Neal

    2016-05-01

    Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.

  20. Microfluidic Screening of Electric Fields for Electroporation.

    Garcia, Paulo A; Ge, Zhifei; Moran, Jeffrey L; Buie, Cullen R

    2016-01-01

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced into the channel in the presence of SYTOX(®), which fluorescently labels cells with compromised membranes. Upon delivery of an electric pulse, the cells fluoresce due to transmembrane influx of SYTOX(®) after disruption of the cell membranes. We calculate the critical electric field by capturing the location within the channel of the increase in fluorescence intensity after electroporation. Bacterial strains with industrial and therapeutic relevance such as Escherichia coli BL21 (3.65 ± 0.09 kV/cm), Corynebacterium glutamicum (5.20 ± 0.20 kV/cm), and Mycobacterium smegmatis (5.56 ± 0.08 kV/cm) have been successfully characterized. Determining the critical electric field for electroporation facilitates the development of electroporation protocols that minimize Joule heating and maximize cell viability. This assay will ultimately enable the genetic transformation of bacteria and archaea considered intractable and difficult-to-transfect, while facilitating fundamental genetic studies on numerous diverse microbes. PMID:26893024

  1. Temperature/electric field scaling in Ferroelectrics

    Hajjaji, Abdelowahed, E-mail: Hajjaji12@gmail.co [Laboratoire de Genie Electrique et Ferroelectricite, LGEF, INSA LYON, Bat. Gustave Ferrie, 69621 Villeurbanne Cedex (France); Guyomar, Daniel; Pruvost, Sebastien [Laboratoire de Genie Electrique et Ferroelectricite, LGEF, INSA LYON, Bat. Gustave Ferrie, 69621 Villeurbanne Cedex (France); Touhtouh, Samira [Laboratoire de Physique de la Matiere Condensee, LPMC, Departement de Physique, Faculte des Sciences, 24000 El-Jadida, Maroc (Morocco); Yuse, Kaori [Laboratoire de Genie Electrique et Ferroelectricite, LGEF, INSA LYON, Bat. Gustave Ferrie, 69621 Villeurbanne Cedex (France); Boughaleb, Yahia [Laboratoire de Physique de la Matiere Condensee, LPMC, Departement de Physique, Faculte des Sciences, 24000 El-Jadida, Maroc (Morocco)

    2010-07-01

    The effects of the field amplitude (E) and temperature on the polarization and their scaling relations were investigated on rhombohedral PMN-xPT ceramics. The scaling law was based on the physical symmetries of the problem and rendered it possible to express the temperature variation ({Delta}{theta}) as an electric field equivalent {Delta}E{sub eq}=({alpha}+2{beta}xP(E,{theta}{sub 0}))x{Delta}{theta}. Consequently, this was also the case for the relationship between the entropy ({Gamma}) and polarization (P). Rhombohedral Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.75}Ti{sub 0.25}O{sub 3} ceramics were used for the verification. It was found that such an approach permitted the prediction of the maximal working temperature, using only purely electrical measurements. It indicates that the working temperature should not exceed 333 K. This value corresponds to the temperature maximum before the dramatic decrease of piezoelectric properties. Reciprocally, the polarization behavior under electrical field can be predicted, using only purely thermal measurements. The scaling law enabled a prediction of the piezoelectric properties (for example, d{sub 31}) under an electrical field replacing the temperature variation ({Delta}{theta}) by {Delta}E/({alpha}+2{beta}xp(E,{theta}{sub 0})). Inversely, predictions of the piezoelectric properties (d{sub 31}) as a function of temperature were permitted using purely only electrical measurements.

  2. Electric field control of the cell orientation

    Westman, Christopher; Sabirianov, Renat

    2008-03-01

    Many physiological processes depend on the response of biological cells to external forces. The natural electric field at a wound controls the orientation of the cell and its division.[1] We model the cell as an elongated elliptical particle with given Young's modulus with surface charge distribution in the external electric field. Using this simple theoretical model that includes the forces due to electrostatics and the elasticity of cells, we calculated analytically the response of the cell orientation and its dynamics in the presence of time varying electric field. The calculations reflect many experimentally observed features. Our model predicts the response of the cellular orientation to a sinusoidally varying applied electric field as a function of frequency similar to recent stress-induced effects.[2] *Bing Song, Min Zhao, John V. Forrester, and Colin D. McCaig, ``Electrical cues regulate the orientation and frequency of cell division and the rate of wound healing in vivo'', PNAS 2002, vol. 99 , 13577-13582. *R. De, A. Zemel, and S.A. Safran, ``Dynamics of cell orientation'', Nature Physics 2007, vol.3, 655.

  3. Microfluidic Screening of Electric Fields for Electroporation

    Garcia, Paulo A.; Ge, Zhifei; Moran, Jeffrey L.; Buie, Cullen R.

    2016-02-01

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced into the channel in the presence of SYTOX®, which fluorescently labels cells with compromised membranes. Upon delivery of an electric pulse, the cells fluoresce due to transmembrane influx of SYTOX® after disruption of the cell membranes. We calculate the critical electric field by capturing the location within the channel of the increase in fluorescence intensity after electroporation. Bacterial strains with industrial and therapeutic relevance such as Escherichia coli BL21 (3.65 ± 0.09 kV/cm), Corynebacterium glutamicum (5.20 ± 0.20 kV/cm), and Mycobacterium smegmatis (5.56 ± 0.08 kV/cm) have been successfully characterized. Determining the critical electric field for electroporation facilitates the development of electroporation protocols that minimize Joule heating and maximize cell viability. This assay will ultimately enable the genetic transformation of bacteria and archaea considered intractable and difficult-to-transfect, while facilitating fundamental genetic studies on numerous diverse microbes.

  4. Physical aspects of magnetic hyperthermia: Low-frequency ac field absorption in a magnetic colloid

    A uniaxially anisotropic superparamagnetic particle suspended in a viscous fluid and subjected to an ac field is considered. Consistently taking into account both internal (Néel) and external (Brownian) magnetic relaxations, a simple expression for the dynamic susceptibility is obtained. This result, with regard to the ac field energy absorption, is compared to the common heuristic approach. This is done for a model polydisperse colloid containing maghemite nanoparticles, which are assumed to posses either bulk or surface magnetic anisotropy. It is shown that viscous losses caused by the particle motion in a fluid matrix make important contribution to the full magnetic response of a ferrocolloid and, thus, its ability to absorb the ac field energy. The obtained exact expression, which takes in both dissipation mechanisms, paves the way to correct optimization of the nanoparticle-mediated heating effect. - Highlights: • A uniaxially anisotropic superparamagnetic particle suspended in a viscous fluid and subjected to an ac field is considered. • Consistently taking into account both internal (Néel) and external (Brownian) magnetic relaxations, a simple expression for the dynamic susceptibility is obtained. • This result, with regard to the ac field energy absorption, is compared to the common heuristic approach using as a benchmark a model polydisperse colloid containing maghemite nanoparticles, which are assumed to posses either bulk or surface magnetic anisotropy. • It is shown that viscous losses caused by the particle motion in a fluid matrix make important contribution to the full magnetic response of a ferrocolloid and, thus, its ability to absorb the ac field energy. • The obtained exact expression, which takes in both dissipation mechanisms, paves the way to correct optimization of the nanoparticle-mediated heating effect

  5. DNA molecular wire-based nanoelectronics: New insight and high frequency AC electrical characterization

    Wibowo, Denni Ari

    While recent research in electron-transport mechanism on a double strands DNA seems to converge into a consensus, experiments in direct electrical measurements on a long DNA molecules still lead to a conflicting result. This research investigates experimentally the attachment of DNA molecular wire to high aspect ratio three-dimensional (3D) metal electrode and the effect of temperature to its AC electrical conductivity. The 3-D microelectrode was built on a silicone oxide substrate using patterned thick layers of negative tone photoresist covered by sputtered gold on the top surface. Attachment of lambda-DNA to the microelectrode was demonstrated using oligonucleotide-DNA phosphate backbone ligation and thiol-gold covalent bonding. Electrical characterizations based on I-V and AC impedance analysis of several repeatable data points of attachment with varying lambda-DNA concentration (500 ng/microL to 0.0625 ng/microL) showed measurable and significant conductivity of lambda-DNA molecular wires. Further study was carried out by measuring I-V and impedance while ramping up the temperature to reach complete denaturation (~1100C) resulting in no current transduction. Subsequent re-annealing of the DNA through incubation in TM buffer at annealing temperature (~900C) resulted in recovery of electrical conduction, providing a strong proof that DNA molecular wire is the one generate the electrical conductivity. lambda-DNA molecular wires reported to have differing impedance response at two temperature regions: impedance increases (conductivity decrease) between 40C -- 400C, and then decreases from 400C until DNA completely denatured (~1100C). The increase conductivity after 400C is an experimental support the long distance electron transport mechanism referred as "thermal hopping" mechanism. We believe that this research represents a significant departure from previous studies and makes unique contributions through (i) modification of DNA attachment methods has increase

  6. Electric field in type II superconductors

    Kolacek, J.; Lipavsky, P.; Spicka, V.

    1999-01-01

    Generally it is accepted that electric field E in type II superconductors is created by the vortex motion, so that it is proportional to the vortex velocity v_L. This assertion is based on the Josephson relation E = - v_L x B, which was derived and is valid if no transport current is present. We present arguments showing that if transport current is present, static electric field is proportional to the relative velocity of vortices in respect to the velocity of superconducting fluid v_s, so t...

  7. Electric Field Quantitative Measurement System and Method

    Generazio, Edward R. (Inventor)

    2016-01-01

    A method and system are provided for making a quantitative measurement of an electric field. A plurality of antennas separated from one another by known distances are arrayed in a region that extends in at least one dimension. A voltage difference between at least one selected pair of antennas is measured. Each voltage difference is divided by the known distance associated with the selected pair of antennas corresponding thereto to generate a resulting quantity. The plurality of resulting quantities defined over the region quantitatively describe an electric field therein.

  8. Electric field effects in RUS measurements.

    Darling, Timothy W; Allured, Bradley; Tencate, James A; Carpenter, Michael A

    2010-02-01

    Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material--a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the "statistical residual" strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods. PMID:19850314

  9. Electric Field Effects in RUS Measurements

    Darling, Timothy W [Los Alamos National Laboratory; Ten Cate, James A [Los Alamos National Laboratory; Allured, Bradley [UNIV NEVADA, RENO; Carpenter, Michael A [CAMBRIDGE UNIV. UK

    2009-09-21

    Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material - a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the 'statistical residual' strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods.

  10. Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields

    Rablau, Corneliu; Lafrance, Joseph; Sala, Anca

    2007-10-01

    We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems.

  11. Study of effect of AC and DC magnetic fields on growth of Pisum sativum seeds

    Bahar, Mahmood; Yasaie Mehrjardi, Yasaman; Sojoodi, Jaleh; Bayani, Hosien; Kazem Salem, Mohammad

    2013-08-01

    This paper concentrates on the effect of the AC and DC magnetic fields on plant growth. The effect of AC magnetic field with intensities of 2.25, 1.66 and 1.49 mT and DC magnetic field with intensities of 3.6, 2.41 and 2.05 mT in exposure durations of 2, 4, 6, 8, 10 and 12 min on two groups of dry and wet Pisum sativum seedlings was studied. In each experiment 10 seeds were used; the experiments were repeated three times for each group and there was a sham exposed group for comparison purposes. The light cycle was 12 h light/12 h darkness and the temperature was 25 ± 1° C. The index of growth is considered to be the root and stem elongation on the sixth day. It was observed that AC magnetic field has a positive effect on the growth in all durations and intensities. Moreover, it is highlighted that during the experiments, the mean growth of dry seedlings significantly increased by a factor of 11 in AC magnetic field with the lowest intensity of 1.49 mT (p effect on the growth of plants in comparison to DC magnetic fields.

  12. DC Electric Fields at the Magnetopause

    Laakso, H. E.; Escoubet, C. P.; Masson, A.

    2014-12-01

    In order to understand the transfer of energy, momentum and mass through the magnetopause one needs to know several plasma and field parameters including the DC electric field which is known to be challenging to measure in tenuous plasma regions, e.g. in the inner side of the magnetopause where the density drops below 1/cc. However, each of the Cluster spacecraft carries five different experiments that can provide information about DC electric fields, i.e. double probe antenna (EFW) and electron drift meter (EDI) as well as electron and ion spectrometers (PEACE, CIS-HIA, CIS-CODIF). Each technique is very different and has its own strengths and limitations. Therefore it is important to compare all available measurements before making a judgement on DC electric field variation at the magnetopause; note that only very rarely all five measurements are available at the same time. Although the full-resolution observations in the Cluster archive are calibrated, they can still contain various errors. However, when two experiments show the same field, it is quite likely that this is the right field because the different measurements are based on so complimentary techniques and the field varies so much when the spacecraft moves from the magnetosheath through the magnetopause into the magnetosphere, or vice versa. In this presentation we present several cases of the magnetopause crossings and how the different measurements agree and disagree around the magnetopause region.

  13. Particle creation by peak electric field

    Adorno, T C; Gitman, D M

    2016-01-01

    The particle creation by the so-called peak electric field is considered. The latter field is a combination of two exponential parts, one exponentially-increasing and another exponentially-decreasing. We find exact solutions of the Dirac equation with the field under consideration with appropriate asymptotic conditions and calculate all the characteristics of particle creation effect, in particular, differential mean numbers of created particle, total number of created particles, and the probability for a vacuum to remain a vacuum. Characteristic asymptotic regimes are discussed in detail and a comparison with the pure asymptotically decaying field is considered.

  14. Analysis on Electric Field Around HVAC-HVDC Hybrid Transmission Lines%Analysis on Electric Field Around HVAC-HVDC Hybrid Transmission Lines

    LI Qian; LIU Jun-xiang; LI Hua; LIN Fu-chang

    2011-01-01

    As the transmission line corridors become more and more rare in China, it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines. The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby. However, few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines. Thus, this research designed a program based on windows, which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively. This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images. For the electric field at ground level under AC transmission line, simula- tion charge method is used, while for the electric field at the ground level under DC transmission lines, deutsch as- sumption method is used. Comparing the results generated by the calculation with those in published literature, the program is reliable. Taking 500 kV transmission lines as an example, when considering the mutual effect of the HVAC-HVDC'lines, the amplitude of the surface voltage gradient will increase by about 10% and the amplitude of the electric field at ground level will increase by about 8%, making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line. Thus, in order to control the electric field at ground level under hybrid lines, it should pay more attention on that produced by the DC line.

  15. Position and movement sensing at metre standoff distances using ambient electric field

    We describe a system for the measurement of changes in electric field which occur as a result of the movement of people, or objects, in ambient electric fields with standoff distances of several metres. A passive sensor system is used to measure the changes in electric field which are due to several different mechanisms. From this we are able to extract presence, movement and position information with a positional accuracy of ∼10 cm. Furthermore, by examining the disturbances in ambient ac fields, such as those created by domestic electricity networks, we show that it is possible to recover static field information with a sensor that lacks dc sensitivity. In this way, we demonstrate that tracking of individuals within large room-scale spaces is possible. As a simple, passive, undetectable technique, with no line of sight requirement, these measurements open up new possibilities in security, telehealth and human computer interfacing applications. (paper)

  16. Causal Analysis of the Inadvertent Contact with an Uncontrolled Electrical Hazardous Energy Source (120 Volts AC)

    David E. James; Dennis E. Raunig; Sean S. Cunningham

    2014-10-01

    On September 25, 2013, a Health Physics Technician (HPT) was performing preparations to support a pneumatic transfer from the HFEF Decon Cell to the Room 130 Glovebox in HFEF, per HFEF OI 3165 section 3.5, Field Preparations. This activity involves an HPT setting up and climbing a portable ladder to remove the 14-C meter probe from above ball valve HBV-7. The HPT source checks the meter and probe and then replaces the probe above HBV-7, which is located above Hood ID# 130 HP. At approximately 13:20, while reaching past the HBV-7 valve position indicator switches in an attempt to place the 14-C meter probe in the desired location, the HPT’s left forearm came in contact with one of the three sets of exposed terminals on the valve position indication switches for HBV 7. This resulted in the HPT receiving an electrical shock from a 120 Volt AC source. Upon moving the arm, following the electrical shock, the HPT noticed two exposed electrical connections on a switch. The HPT then notified the HFEF HPT Supervisor, who in turn notified the MFC Radiological Controls Manager and HFEF Operations Manager of the situation. Work was stopped in the area and the hazard was roped off and posted to prevent access to the hazard. The HPT was escorted by the HPT Supervisor to the MFC Dispensary and then preceded to CFA medical for further evaluation. The individual was evaluated and released without any medical restrictions. Causal Factor (Root Cause) A3B3C01/A5B2C08: - Knowledge based error/Attention was given to wrong issues - Written Communication content LTA, Incomplete/situation not covered The Causal Factor (root cause) was attention being given to the wrong issues during the creation, reviews, verifications, and actual performance of HFEF OI-3165, which covers the need to perform the weekly source check and ensure placement of the probe prior to performing a “rabbit” transfer. This resulted in the hazard not being identified and mitigated in the procedure. Work activities

  17. Atomic emission spectroscopy in high electric fields

    Bailey, J.E.; Filuk, A.B.; Carlson, A.L. [and others

    1995-12-31

    Pulsed-power driven ion diodes generating quasi-static, {approximately}10 MV/cm, 1-cm scale-length electric fields are used to accelerate lithium ion beams for inertial confinement fusion applications. Atomic emission spectroscopy measurements contribute to understanding the acceleration gap physics, in particular by combining time- and space-resolved measurements of the electric field with the Poisson equation to determine the charged particle distributions. This unique high-field configuration also offers the possibility to advance basic atomic physics, for example by testing calculations of the Stark-shifted emission pattern, by measuring field ionization rates for tightly-bound low-principal-quantum-number levels, and by measuring transition-probability quenching.

  18. Atomic emission spectroscopy in high electric fields

    Pulsed-power driven ion diodes generating quasi-static, ∼10 MV/cm, 1-cm scale-length electric fields are used to accelerate lithium ion beams for inertial confinement fusion applications. Atomic emission spectroscopy measurements contribute to understanding the acceleration gap physics, in particular by combining time- and space-resolved measurements of the electric field with the Poisson equation to determine the charged particle distributions. This unique high-field configuration also offers the possibility to advance basic atomic physics, for example by testing calculations of the Stark-shifted emission pattern, by measuring field ionization rates for tightly-bound low-principal-quantum-number levels, and by measuring transition-probability quenching

  19. Surface superconductivity controlled by electric field

    We discuss an effect of the electrostatic field on superconductivity near the surface. First, we use the microscopic theory of de Gennes to show that the electric field changes the boundary condition for the Ginzburg-Landau function. Second, the effect of the electric field is evaluated in the vicinity of Hc3, where the boundary condition plays a crucial role.We predict that the field effect on the surface superconductivity leads to a discontinuity of the magnetocapacitance. We estimate that the predicted discontinuity is accessible for nowadays experimental tools and materials. It is shown that the magnitude of this discontinuity can be used to predict the dependence of the critical temperature on the charge carrier density which can be tailored by doping.

  20. Electric field effects on phase transitions in the 8CB liquid crystal doped with ferroelectric nanoparticles

    Lin, Y.; Daoudi, A.; Segovia-Mera, A.; Dubois, F.; Legrand, C.; Douali, R.

    2016-06-01

    The influence of a low ac electric field on phase transitions is discussed in the case of a nematic liquid crystal 4 -n -octyl-4 '-cyanobiphenyl (8CB) doped with Sn2P2S6 ferroelectric nanoparticles. The phase-transition temperatures obtained from temperature-dependent dielectric measurements were higher than those determined by the calorimetric method. This difference is explained by the presence of the measuring electric field which induces two effects. The first one is the amplification of the interactions between the nanoparticle polarization and the liquid-crystal order parameter. The second one is the field-induced disaggregation or aggregation process at high nanoparticle concentrations.

  1. Electric-field-assisted convective assembly of colloidal crystal coatings.

    Kleinert, Jairus; Kim, Sejong; Velev, Orlin D

    2010-06-15

    A new technique that combines evaporative convective deposition of colloidal crystal coatings with an electric field to achieve more rapid assembly and reduce the defects in the crystal structure is reported. When an ac voltage is applied across the particle suspension and the substrate in the convective assembly process, a longer film spreads from the meniscus by the electrowetting-on-dielectric (EWOD) effect. The data suggest that the EWOD-increased liquid surface area results in increased evaporation-driven particle flux and crystal assembly that is up to five times more rapid. The extended drying film also provides more time for particle rearrangement before the structure becomes fixed, resulting in formation of crystal domains an order of magnitude larger than those deposited by convective assembly alone. The results demonstrate that EWOD is a facile tool for controlling particle assembly processes in wetting films. The technique could be used in improved large-scale colloidal crystal coating processes. PMID:20465234

  2. Superposition of an AC field improves the discrimination between peptides in nanopore analysis.

    Jakova, Elisabet; Lee, Jeremy S

    2015-07-21

    In standard nanopore analysis a constant DC voltage is used to electrophoretically drive small molecules and peptides towards a pore. Superposition of an AC voltage at particular frequencies causes molecules to oscillate as they approach the pore which can alter the event parameters, the blockade current (I) and blockade time (T). Four peptides with similar structures were studied. Alpha-helical peptides A10 (FmocDDA10KK), A14, A18 and retro-inverso A10. It was shown that the ratio of translocations to bumping events could be manipulated by a combination of AC voltages and frequencies. In particular, A10 could be studied without interference from retro-inverso A10. Similarly, a large, intrinsically disordered protein of 140 amino acids, α-synuclein, which translocates the pore readily in a DC field could be prevented from doing so by application of an AC field of 200 mV at 100 MHz. PMID:25699656

  3. Interaction of electric and hydrodynamic fields

    Ostroumov, G.A.

    1979-01-01

    A systematic presentation is made of the basic electrophysical and hydromechanical characteristics that are responsible for the processes of heat and mass exchange in insulating fluids that are found in strong electric fields. Recommendations are made with respect to the intensification of these processes as well as to their use in science and technology. Promising topics for future research are indicated. The introduction lists two ways that lead to the elaboration of two concepts that are essential to electrohydrodynamics - electrochemical and electro-power engineering. The first four chapters deal with a study of pondermotive forces in immobile media. The fifth chapter presents experimental material on electric wind in gases. Information is also given on electric wind in fluids and a theoretical interpretation of this phenomenon, and on results of experimental and theoretical studies of electric breakdown of fluids. 200 references, 108 figures, 12 tables.

  4. Motional Spin Relaxation in Large Electric Fields

    Schmid, Riccardo; Filippone, B W

    2008-01-01

    We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}\\mathrm{He}$ atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}\\mathrm{He}$ samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}\\mathrm{He}$ atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}\\mathrm{He}$ atoms at temperatures below $600 \\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, ...

  5. Vacuum interface flashover with bipolar electric fields

    Tucker, W.K.; Anderson, R.A.; Hasti, D.E.; Jones, E.E.; Bennett, L.F.

    1985-05-01

    High energy, compact, particle accelerators require accelerating cavities that have large gradients and operate with high efficiency. The bipolar electric fields required in these efficient accelerating cavities place severe requirements on the vacuum interface. Experimentally, we have found that the bipolar flashover field varies as t/sup -1/2/ for times out to 300 ns and then remains essentially constant at 33 kV/cm for longer duration waveforms, whereas materials subjected to unipolar electric fields follow a t/sup -1/6/ relationship. Furthermore, specific accelerating cavities offer enhancements that may be employed to achieve highly uniform electric fields across the vacuum interface. Using these results and the results of a previously developed theory of unipolar flashover, a new interface has been designed and 50 kV/cm bipolar flashover field achieved for a waveform train that lasted 1 ..mu..s. This paper will discuss the design of this vacuum interface and the evaluation of various materials that led to achieving bipolar flashover fields 50% greater than we had previously obtained for long duration waveforms. 10 refs., 6 figs.

  6. Vacuum interface flashover with bipolar electric fields

    High energy, compact, particle accelerators require accelerating cavities that have large gradients and operate with high efficiency. The bipolar electric fields required in these efficient accelerating cavities place severe requirements on the vacuum interface. Experimentally, we have found that the bipolar flashover field varies as t/sup -1/2/ for times out to 300 ns and then remains essentially constant at 33 kV/cm for longer duration waveforms, whereas materials subjected to unipolar electric fields follow a t/sup -1/6/ relationship. Furthermore, specific accelerating cavities offer enhancements that may be employed to achieve highly uniform electric fields across the vacuum interface. Using these results and the results of a previously developed theory of unipolar flashover, a new interface has been designed and 50 kV/cm bipolar flashover field achieved for a waveform train that lasted 1 μs. This paper will discuss the design of this vacuum interface and the evaluation of various materials that led to achieving bipolar flashover fields 50% greater than we had previously obtained for long duration waveforms. 10 refs., 6 figs

  7. Modelling electricity forward markets by ambit fields

    Barndorff-Nielsen, Ole; Fred Espen Benth, Fred Espen; Veraart, Almut

    This paper proposes a new modelling framework for electricity forward markets, which is based on ambit fields. The new model can capture many of the stylised facts observed in energy markets. One of the main differences to the traditional models lies in the fact that we do not model the dynamics...

  8. Plasma instabilities in high electric fields

    Morawetz, K.; Jauho, Antti-Pekka

    1994-01-01

    expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  9. High voltage electric field effects on structure and biological characteristics of barley seeds

    Khazaei, J. [Tehran Univ., Tehran (Iran, Islamic Republic of). Dept. of Agrotechnology, Univ. College of Abouraihan; Aliabadi, E. [Tehran Univ., Tehran (Iran, Islamic Republic of). Dept. of Crop Production Horticulture, Univ. College of Aburaihan; Shayegani, A.A. [Tehran Univ., Tehran (Iran, Islamic Republic of). Univ. College of Engineering

    2010-07-01

    Electric biostimulation of seeds is a pre-sowing treatment in which an electric field is applied to seeds to increase germination of non standard seeds. This paper reported on a study that examined the effects of AC electric field and exposure time on the structure and biological characteristics of barley seeds. The objective was to determine the potential to accelerate seed germination, plant growth and root development by the electric field strength and exposure time. Makooei cultivar barley seeds were used in this study. The effect of electric field strength (at 2, 4, 9, and 14 kV/m) and exposure time (at 15, 45, 80, and 150 min) on seed germination was studied along with height of seedling, length or root, height of stem, length of leaves, earliness, dry weight and wet weight of seedling. The treated seeds were stored for a month in a refrigerator at 5 degrees C prior to the germination experiments. The initial germination percent of the seed was 81 per cent. The treatment of barley seeds in an AC electric field had a positive effect on all investigated parameters. The germination percent of the treated seed increased to 94.5 per cent . The seeds exposed for long periods of time (45 to 150 min) showed better germination than the seeds exposed to lower exposure times. Dry and wet weights of seedling increased 143.4 per cent and 45.7 per cent, respectively.

  10. A.c. magnetic-field measurements using the fluxgate

    Ripka, Pavel; Primdahl, Fritz; Nielsen, Otto V;

    1995-01-01

    Fluxgate sensors are mostly used in closed-loop d.c. magnetometer systems; they can also measure alternating fields up to severalkilohertz, either in open-loop mode or from an error signal in the slow-feedback loop as in the Thunderstorm rocket magnetometer, which has 0.1 nT resolution up to 3 k...

  11. Field-aligned currents and ionospheric electric fields

    Yasuhara, F.; Akasofu, S.-I.

    1977-01-01

    It is shown that the observed distribution of the ionospheric electric field can be deduced from an equation combining Ohm's law with the current continuity equation by using the 'observed' distribution of field-aligned currents as the boundary condition for two models of the ionosphere. The first model has one conductive annular ring representing the quiet-time auroral precipitation belt; the second has two conductive annular rings that simulate the discrete and diffuse auroral regions. An analysis is performed to determine how well the electric-field distribution can be reproduced. The results indicate that the first model reproduces the Sq(p)-type distribution, the second model reproduces reasonably well a substorm-type potential and ionospheric current patterns together with the Harang discontinuity, and that the distribution of field-aligned currents is the same for both models.

  12. Vacuum interface flashover with bipolar electric fields

    High energy, compact, particle accelerators require accelerating cavities that have large gradients and operate with high efficiency. The bipolar electric fields necessary in these efficient accelerating cavities place severe requirements on the insulator-vacuum interface. A new interface has been designed and 50 gv/cm bipolar flashover field achieved for a waveform train that lasted 1 μs. This paper discusses the design of this vacuum interface and the evaluation of various materials that led to achieving bipolar flashover fields 50% greater than the authors had previously obtained

  13. Effects of AC magnetic field and carboxymethyldextran-coated magnetite nanoparticles on mice peritoneal cells

    A portable apparatus was developed to perform magnetohyperthermia (MHT) assays. In order to investigate its efficiency on cell lysis, biological effects of the AC magnetic field exposure after carboxymethyldextran-coated magnetite-nanoparticles (CMDC) treatment were investigated. Phagocyte capacity, cell viability, and morphology data evidenced that the CMDC sample and the apparatus are useful to further investigate MHT in cancer therapy

  14. Effects of AC magnetic field and carboxymethyldextran-coated magnetite nanoparticles on mice peritoneal cells

    Araujo Guedes, Maria Helena [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Sadeghiani, Neda [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Lima Guedes Peixoto, Danielle [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Poubel Coelho, Julia [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Santos Barbosa, Luzirlane [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Bentes Azevedo, Ricardo [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Kueckelhaus, Selma [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil); Faculdade de Medicina, Universidade de Brasilia, Area de Morfologia, 70910-900 Brasilia-DF (Brazil); Silva, Maria de Fatima da [Nucleo de Fisica Aplicada, Instituto de Fisica, Universidade de Brasilia, 70919-970 Brasilia-DF (Brazil); Morais, Paulo Cesar [Nucleo de Fisica Aplicada, Instituto de Fisica, Universidade de Brasilia, 70919-970 Brasilia-DF (Brazil); Guerrero Marques Lacava, Zulmira [Depto de Genetica e Morfologia, Instituto de Ciencias Biologicas, Universidade de Brasilia, 70910-900 Brasilia-DF (Brazil)]. E-mail: zulmira@unb.br

    2005-05-15

    A portable apparatus was developed to perform magnetohyperthermia (MHT) assays. In order to investigate its efficiency on cell lysis, biological effects of the AC magnetic field exposure after carboxymethyldextran-coated magnetite-nanoparticles (CMDC) treatment were investigated. Phagocyte capacity, cell viability, and morphology data evidenced that the CMDC sample and the apparatus are useful to further investigate MHT in cancer therapy.

  15. Influence of electric field on cellular migration

    Guido, Isabella; Bodenschatz, Eberhard

    Cells have the ability to detect continuous current electric fields (EFs) and respond to them with a directed migratory movement. Dictyostelium discoideum (D.d.) cells, a key model organism for the study of eukaryotic chemotaxis, orient and migrate toward the cathode under the influence of an EF. The underlying sensing mechanism and whether it is shared by the chemotactic response pathway remains unknown. Whereas genes and proteins that mediate the electric sensing as well as that define the migration direction have been previously investigated in D.d. cells, a deeper knowledge about the cellular kinematic effects caused by the EF is still lacking. Here we show that besides triggering a directional bias the electric field influences the cellular kinematics by accelerating the movement of cells along their path. We found that the migratory velocity of the cells in an EF increases linearly with the exposure time. Through the analysis of the PI3K and Phg2 distribution in the cytosol and of the cellular adherence to the substrate we aim at elucidating whereas this speed up effect in the electric field is due to either a molecular signalling or the interaction with the substrate. This work is part of the MaxSynBio Consortium which is jointly funded by the Federal Ministry of Education and Research of Germany and the Max Planck Society.

  16. Quantum inductive circuits under ac and dc fields: Current manifestations of charge discreteness

    It is well known that the electrical current of a quantum inductive circuits with charge discreteness qe displays Bloch-like oscillations (frequency ωB=qeεd-bar ) under a dc external voltage (εd). Here we consider the effect of a superposed ac voltage in the circuit. Resonances are explicitly found. In the limit of small external frequency (ω-bar ωB), the electrical (one-period-averaged) current exist and has always the same sign. This gives us an experimental method to measure discrete charge effects in (quantum) nanometric circuits since the established current is depending on charge discreteness

  17. Acquisition of Cry1Ac Protein by Non-Target Arthropods in Bt Soybean Fields

    Huilin Yu; Jörg Romeis; Yunhe Li; Xiangju Li; Kongming Wu

    2014-01-01

    Soybean tissue and arthropods were collected in Bt soybean fields in China at different times during the growing season to investigate the exposure of arthropods to the plant-produced Cry1Ac toxin and the transmission of the toxin within the food web. Samples from 52 arthropod species/taxa belonging to 42 families in 10 orders were analysed for their Cry1Ac content using enzyme-linked immunosorbent assay (ELISA). Among the 22 species/taxa for which three samples were analysed, toxin concentra...

  18. DC and AC linear magnetic field sensor based on glass coated amorphous microwires with Giant Magnetoimpedance

    Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe6Co94)72.5Si12.5B15. The impedance of a 1.5 cm length sample has been characterized by using constant AC currents in the range of 400 µA–4 mA at frequencies from 7 to 15 MHz and DC magnetic fields from −900 to 900 A/m. Double peak responses have been obtained, showing GMI ratios up to 107%. A linear magnetic field sensor for DC and AC field has been designed, using two microwires connected in series with a magnetic bias of 400 A/m with opposite direction in each microwire in order to obtain a linear response from ±70 (A/m)rms for AC magnetic field, and ±100 A/m for DC magnetic field. A closed loop feedback circuit has been implemented to extend the linear range to ±1 kA/m for DC magnetic field. - Highlights: • Giant Magneto Impedance phenomenon has been studied in amorphous microwires. • A combination of two microwires with a bias field has been developed to get a linear response. • An electronic circuit has been developed to obtain a sensor with a linear response. • A feedback coil have been added to increase the measurable range of the sensor

  19. Nanoscale and macroscopic electrical ac transport along conductive domain walls in lithium niobate single crystals

    The electrical impedance properties of UV-illuminated (λ = 310 nm) charged, conductive domain walls (CDWs) in 5 mol% magnesium-doped lithium niobate (LNO) single crystals are investigated on the nm-length scale using nanoimpedance microscopy (NIM) as well as by comparing the macroscopically measured complex impedance response between multi- and single-domain LNO samples. Similar to the case of dc conductivity, a higher conductivity of domain walls (DWs) compared to the bulk insulating matrix was observed. The contrast between DWs and bulk is most pronounced at lower frequencies (f < 200 Hz) due to the large bulk capacitance at higher frequencies. Moreover, the simultaneous application of both an ac and dc bias results in an increased real part of the ac DW current. Also, equivalent circuits accurately describing both the domain and CDW contributions were developed; as a result we are able to analyze and quantify the complex dielectric conductive behavior of both bulk and CDWs in LNO within the framework of the mixed conduction model. Hopping of excited charge carriers along the CDWs was identified as the dominant charge transport process. (paper)

  20. Electrical properties of a piezoelectric transformer for an AC-DC converter

    The electrical properties of a ring/dot piezoelectric transformer were analyzed for applications as an AC-DC converter using the step-down behavior of a piezoelectric transformer. The ring/dot piezoelectric transformer was prepared using Pb(Mn1/3Nb2/3)O3 and Pb(Zn1/3Nb2/3)O3 modified Pb(Zr,Ti)O3 ceramics sintered at a relatively low temperature of 930 .deg. C for 90 min. When the transformer was matched with a load resistance of 1000 Ω, it transferred a maximum power of 27 W. The maximum power was produced at a dc output voltage of 30 V and a matching load resistance of 1000 Ω. While the manufactured ring/dot piezoelectric transformer released the maximum power at a resonance frequency of 71 kHz, the available frequency bandwidth was about 1 kHz at most due to strong frequency dependence of the piezoelectric transformer. The output dc current was highly improved up to 905 mA because no anisotropy of poling direction existed in the ring/dot piezoelectric transformer. Under a commercial input of 220 Vac, AC-DC converter successfully produced 27 W at 30 Vdc and 905 mA.

  1. Truthful Complex-valued Knapsack Problem and Discrete Optimization in A/C Electrical Grid

    Chau, Chi-Kin

    2012-01-01

    Since efficient power allocation is a critical requirement for smart grid, we study an important basic setting -- "knapsack problem with selfish users", whereby we design a mechanism to find a utility-maximizing allocation for a group of users with inelastic demands, such that users truthfully reveal their private utility information. As a departure from the traditional setting, complex-valued entities (e.g. power, voltage, and current) are common in A/C electrical grid. There were only few results in the literature concerning complex-valued entities for discrete optimization, because they are substantially more challenging. In this paper, we introduce a non-trivial generalization of knapsack problem with a complex-valued constraint on A/C power, which casts fundamental insight to discrete optimization for smart grid. We provide results of approximability (the existence of a (1/2- e-approximation algorithm) and inapproximability (the absence of FPTAS unless P = NP) for a class of complex-valued knapsack probl...

  2. Dielectrophoretic manipulation of macromolecules: The electric field

    The use of dielectrophoresis is fast becoming a proven technique for manipulating particles and macromolecules in microfluidic systems. Here an analytic solution for the gradient in the electric field strength, {nable}·(E·E), produced by a two-dimensional array of parallel electodes is derived using the method of Green's functions. The boundary condition for the potential between electrodes is estimated by using a linear approximation. While the Green's function used here is somewhat different from Wang , J. Phys. D 29, 1649 (1996), the resulting analytic expression for the potential field is in exact agreement with their result. Selected results for equispaced electrodes with equal widths are compared with Wang , J. Phys. D 29, 1649 (1996). The analytic solution is employed to study the effects of electrode spacing and electrode width on the gradient in electric field intensity. Results show that the magnitude in the gradient in the electric field intensity exhibited the expected dependence on the applied voltage; however, the dependence on electrode width was found to be on the order of the electrode width squared. Results to explore the effects of electrode spacing show that as the spacing is reduced below two electrode widths the magnitude of the gradient increases exponentially

  3. Broken space-time symmetries and mechanisms of rectification of ac fields by nonlinear (non)adiabatic response

    Denisov, S.; Flach, S.; Ovchinnikov, A. A.;

    2002-01-01

    We consider low-dimensional dynamical systems exposed to a heat bath and to additional ac fields. The presence of these ac fields may lead to a breaking of certain spatial or temporal symmetries, which in turn cause nonzero averages of relevant observables. Nonlinear (non)adiabatic response...

  4. On the optical and electrical properties of rf and a.c. plasma polymerized aniline thin films

    U S Sajeev; C Joseph Mathai; S Saravanan; Rajeev R Ashokan; S Venkatachalam; M R Anantharaman

    2006-04-01

    Polyaniline is a widely studied conducting polymer and is a useful material in its bulk and thin film form for many applications, because of its excellent optical and electrical properties. Pristine and iodine doped polyaniline thin films were prepared by a.c. and rf plasma polymerization techniques separately for the comparison of their optical and electrical properties. Doping of iodine was effected in situ. The structural properties of these films were evaluated by FTIR spectroscopy and the optical band gap was estimated from UV-vis-NIR measurements. Comparative studies on the structural, optical and electrical properties of a.c. and rf polymerization are presented here. It has been found that the optical band gap of the polyaniline thin films prepared by rf and a.c. plasma polymerization techniques differ considerably and the band gap is further reduced by in situ doping of iodine. The electrical conductivity measurements on these films show a higher value of electrical conductivity in the case of rf plasma polymerized thin films when compared to the a.c. plasma polymerized films. Also, it is found that the iodine doping enhanced conductivity of the polymer thin films considerably. The results are compared and correlated and have been explained with respect to the different structures adopted under these two preparation techniques.

  5. Hall-Effect Based Semi-Fast AC On-Board Charging Equipment for Electric Vehicles

    Eva González-Romera

    2011-09-01

    Full Text Available The expected increase in the penetration of electric vehicles (EV and plug-in hybrid electric vehicles (PHEV will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V mode, and also in vehicle-to-grid (V2G mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented.

  6. Hall-effect based semi-fast AC on-board charging equipment for electric vehicles.

    Milanés-Montero, María Isabel; Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; González-Romera, Eva

    2011-01-01

    The expected increase in the penetration of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) will produce unbalanced conditions, reactive power consumption and current harmonics drawn by the battery charging equipment, causing a great impact on the power quality of the future smart grid. A single-phase semi-fast electric vehicle battery charger is proposed in this paper. This ac on-board charging equipment can operate in grid-to-vehicle (G2V) mode, and also in vehicle-to-grid (V2G) mode, transferring the battery energy to the grid when the vehicle is parked. The charger is controlled with a Perfect Harmonic Cancellation (PHC) strategy, contributing to improve the grid power quality, since the current demanded or injected has no harmonic content and a high power factor. Hall-effect current and voltage transducers have been used in the sensor stage to carry out this control strategy. Experimental results with a laboratory prototype are presented. PMID:22163697

  7. A.c. magnetic-field measurements using the fluxgate

    Ripka, Pavel; Primdahl, Fritz; Nielsen, Otto V; Petersen, Jan Raagaard; Ranta, Aarne

    Fluxgate sensors are mostly used in closed-loop d.c. magnetometer systems; they can also measure alternating fields up to severalkilohertz, either in open-loop mode or from an error signal in the slow-feedback loop as in the Thunderstorm rocket magnetometer, which has 0.1 nT resolution up to 3 k......Hz. The alternative is to use the direct induction effect in the pick-up or feedback coil. While the low L/R constant of thepick-up coil causes a high -3 dB frequency corner, the spherical feedback coil has a narrow frequency characteristics and low noise up to 10 kHz when used as a search coil. The noise...

  8. Experimental demonstration of electric field tomography

    Electric field tomography (EFT) has recently been introduced in theory. It is a new kind of quasistatic tomography suitable for contactless imaging of biological tissues. Single-channel measurements have already proven the theory. Herein the first multi-channel measuring system for EFT is presented. Experiments on imaging of a test object with different geometries are described. The first EFT images obtained experimentally have been demonstrated and discussed

  9. Anisotropic donor states in electric field

    Zakrzewski, Adam J. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland)

    2009-06-15

    In this paper we consider the application of the stabilization method to calculations of the ground state energy and resonance width of shallow donors in a uniform electric field. We show for the first time that within our formulation of this method it is very easy to include various factors influencing electronic structure of shallow impurities, like effective mass anisotropy or magnetic field. We demonstrate that the effective mass anisotropy significantly changes the lifetime of donor bound electrons. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    Kajikawa, K., E-mail: kajikawa@sc.kyushu-u.ac.j [Research Institute of Superconductor Science and Systems, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Funaki, K. [Research Institute of Superconductor Science and Systems, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Shikimachi, K.; Hirano, N.; Nagaya, S. [Chubu Electric Power Co., Inc., 20-1 Kitasekiyama, Ohdaka-cho, Midori-ku, Nagoya 459-8522 (Japan)

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean's critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  11. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  12. Mott insulators in strong electric fields

    Recent experiments on ultracold atomic gases in an optical lattice potential have produced a Mott insulating state of 87Rb atoms. This state is stable to a small applied potential gradient (an 'electric' field), but a resonant response was observed when the potential energy drop per lattice spacing (E), was close to the repulsive interaction energy (U) between two atoms in the same lattice potential well. We identify all states which are resonantly coupled to the Mott insulator for E≅U via an infinitesimal tunneling amplitude between neighboring potential wells. The strong correlation between these states is described by an effective Hamiltonian for the resonant subspace. This Hamiltonian exhibits quantum phase transitions associated with an Ising density wave order and with the appearance of superfluidity in the directions transverse to the electric field. We suggest that the observed resonant response is related to these transitions and propose experiments to directly detect the order parameters. The generalizations to electric fields applied in different directions and to a variety of lattices should allow study of numerous other correlated quantum phases

  13. Spin generation by strong inhomogeneous electric fields

    Finkler, Ilya; Engel, Hans-Andreas; Rashba, Emmanuel; Halperin, Bertrand

    2007-03-01

    Motivated by recent experiments [1], we propose a model with extrinsic spin-orbit interaction, where an inhomogeneous electric field E in the x-y plane can give rise, through nonlinear effects, to a spin polarization with non-zero sz, away from the sample boundaries. The field E induces a spin current js^z= z x(αjc+βE), where jc=σE is the charge current, and the two terms represent,respectively, the skew scattering and side-jump contributions. [2]. The coefficients α and β are assumed to be E- independent, but conductivity σ is field dependent. We find the spin density sz by solving the equation for spin diffusion and relaxation with a source term ∇.js^z. For sufficiently low fields, jc is linear in E, and the source term vanishes, implying that sz=0 away from the edges. However, for large fields, σ varies with E. Solving the diffusion equation in a T-shaped geometry, where the electric current propagates along the main channel, we find spin accumulation near the entrance of the side channel, similar to experimental findings [1]. Also, we present a toy model where spin accumulation away from the boundary results from a nonlinear and anisotropic conductivity. [1] V. Sih, et al, Phys. Rev. Lett. 97, 096605 (2006). [2] H.-A. Engel, B.I. Halperin, E.I.Rashba, Phys. Rev. Lett. 95, 166605 (2005).

  14. Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field

    Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

    2014-09-01

    An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

  15. Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field.

    Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

    2014-09-01

    An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field. PMID:25314449

  16. Very high field magnetization and AC susceptibility of native horse spleen ferritin

    Guertin, R.P. [Department of Physics and Astronomy, Room 201, Science and Technology Center, Tufts University, Medford, MA 02155 (United States)]. E-mail: robert.guertin@tufts.edu; Harrison, N. [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Zhou, Z.X. [MS6056, Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States); McCall, S. [Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94551 (United States); Drymiotis, F. [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States)

    2007-01-15

    The magnetization of native horse spleen ferritin protein is measured in pulsed magnetic fields to 55 T at T=1.52 K. The magnetization rises smoothly with negative curvature due to uncompensated Fe{sup 3+} spins and with a large high field slope due to the underlying antiferromagnetic ferritin core. Even at highest fields the magnetic moment is only {approx}4% of the saturation moment of the full complement of Fe{sup 3+} in the ferritin molecule. The AC magnetic susceptibility, {chi} {sub AC}(T,f), responding to the uncompensated spins, reaches a maximum near the superparamagnetic blocking temperature with the temperature of the maximum, T {sub M}, varying with excitation frequency, T {sub M} {sup -1} {alpha} log f for 10{<=}f{<=}10{sup 4} Hz.

  17. Contaminación acústica por grupos electrógenos // Acoustic contamination by diesel driven electric plant.

    Yanexy Cepero-Aguilera

    2009-05-01

    Full Text Available El trabajo tiene como tema el impacto ambiental por ruido de grupos electrógenos (GE. Semuestran diferentes definiciones y conceptos referidos a la explotación de los GE y lasconsecuencias que puede provocar a las personas que permanezcan cerca de ellos durante sufuncionamiento. Los grupos electrógenos son además de generadores de energía, generadores deruido y por tanto contribuyen a la contaminación acústica del lugar donde estén situados. En eldocumento se aborda la importancia del correcto uso y selección de los protectores auditivos paraaquellas personas que trabajen directamente en las baterías de grupos electrógenos, así comoalgunas formas de atenuar el ruido. También se caracteriza la emisión sonora de estos a partir deestudios realizados.Palabras claves: ruido, nivel sonoro, sonido.________________________________________________________________________AbstractThis paper concerns with the environmental damage due to noise emission introduced by EngineGenerator Sets. Definitions and concepts about Engine Generator operation are shown as well asthe consequences over the personnel who stand near the Engine Generators during theiroperation. Obviously, such kind of machines generates energy but they also generate noise whichcontaminates the environment around them. The paper states how important are the rightselection and use of noise protection devices for those whose main job is to operate enginegenerator sets. Some methods for noise damping are also shown. Finally, some case studies arepresented in order to describe the noise emission registered in the real world.Key words: noise, sound level, sound.

  18. Nonlinear ac conductivity of interacting 1d electron systems

    Rosenow, Bernd; Nattermann, Thomas

    2004-01-01

    We consider low energy charge transport in one-dimensional (1d) electron systems with short range interactions under the influence of a random potential. Combining RG and instanton methods, we calculate the nonlinear ac conductivity and discuss the crossover between the nonanalytic field dependence of the electric current at zero frequency and the linear ac conductivity at small electric fields and finite frequency.

  19. Calculation of electric fields in imperfect dielectrics

    Filippov, A.A.

    1985-07-01

    No existing numerical method of calculating electric fields in kinetical form allows simultaneous consideration of bias current and conductivity current. This article suggests a modification of the method of integral equations allowing computation of the field in imperfect media. The use of the method is said to be more effective than the method of equivalent discharges. The method suggested allows computation of the field while simultaneously considering conductivity current and permeability current. It also allows determination of the frequency characteristics of high voltage apparatus. Furthermore, it can be used to calculate various transient processes if the applied voltage is expanded into a Fourier series and calculations are performed individually for each member of the series.

  20. Spontaneous electric fields in solid films: spontelectrics

    Field, David; Plekan, Oksana; Cassidy, Andrew;

    2013-01-01

    When dipolar gases are condensed at sufficiently low temperature onto a solid surface, they form films that may spontaneously exhibit electric fields in excess of 108V/m. This effect, called the ‘spontelectric effect’, was recently revealed using an instrument designed to measure scattering...... that the spontelectric field generally decreases monotonically with increased deposition temperature, with the exception of methyl formate that shows an increase beyond a critical range of deposition temperature. Films of spontelectric material show a Curie temperature above which the spontelectric effect disappears....... Heterolayers may also be laid down creating potential wells on the nanoscale. A model is put forward based upon competition between dipole alignment and thermal disorder, which is successful in reproducing the variation of the degree of dipole alignment and the spontelectric field with deposition temperature...

  1. Electron transport in argon in crossed electric and magnetic fields

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field. PMID:11088933

  2. Possible control scenario of radial electric field by loss-cone-particle injection into helical device

    The possibility of controlling the radial electric field of toroidal plasmas by injecting high energy electrons along the reversible loss cone orbit of the helical magnetic traps is investigated. It is well known that the radial electric field plays an important role in the confinement improvement scenario especially in the low collisional regime under the physics picture of neoclassical theory. For this purpose, it is made clear that the most suitable particles are transit particles, which show a transition from helically trapped orbits to blocked ones. It is also found that a parallel AC electric field launched from outside assists this transition and makes it possible for particles to penetrate deeply into the plasma. In addition we clarify that the viscosity of the plasma coupled with the helical field configuration provide a bifurcation of plasma states and its stable solution results in confinement improvement. (author)

  3. Effects of AC magnetic field on spin-exchange relaxation of atomic magnetometer

    Lu, Jixi; Qian, Zheng; Fang, Jiancheng; Quan, Wei

    2016-03-01

    By operating at high alkali-metal densities and in low magnetic fields, the spin-exchange relaxation of atomic magnetometers can be eliminated, allowing construction of ultra-high sensitive spin-exchange relaxation-free magnetometers. Significant AC magnetic fields are usually introduced in the magnetometer by the magnetic field modulation technique or the cell heater, whose effects on the spin-exchange relaxation have not been evaluated. In this paper, we study experimentally the spin-exchange relaxation rate as a function of the magnetic field frequency, the magnetic field amplitude and the spin-exchange rate in low magnetic fields. The experimental results indicate that for low atomic polarization the spin-exchange relaxation rate decays exponentially with the magnetic field frequency, and the reciprocal of the decay constant is proportional to the spin-exchange rate.

  4. Contaminación acústica por grupos electrógenos

    Yanexy Cepero-Aguilera

    2009-05-01

    Full Text Available El trabajo tiene como tema el impacto ambiental por ruido de grupos electrógenos (GE. Se muestran diferentes definiciones y conceptos referidos a la explotación de los GE y las consecuencias que puede provocar a las personas que permanezcan cerca de ellos durante su funcionamiento. Los grupos electrógenos son además de generadores de energía, generadores de ruido y por tanto contribuyen a la contaminación acústica del lugar donde estén situados. En el documento se aborda la importancia del correcto uso y selección de los protectores auditivos para aquellas personas que trabajen directamente en las baterías de grupos electrógenos, así como algunas formas de atenuar el ruido. También se caracteriza la emisión sonora de estos a partir de estudios realizados.This paper concerns with the environmental damage due to noise emission introduced by Engine Generator Sets. Definitions and concepts about Engine Generator operation are shown as well as the consequences over the personnel who stand near the Engine Generators during their operation. Obviously, such kind of machines generates energy but they also generate noise which contaminates the environment around them. The paper states how important are the right selection and use of noise protection devices for those whose main job is to operate engine generator sets. Some methods for noise damping are also shown. Finally, some case studies are presented in order to describe the noise emission registered in the real world.

  5. Observations of large transient magnetospheric electric fields

    Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine clearly defined, exceptionally large-amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to 5.5 R/sub e/ at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicate a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity

  6. Local-gated single-walled carbon nanotube field effect transistors assembled by AC dielectrophoresis

    Stokes, Paul; Khondaker, Saiful I.

    2007-01-01

    We present a simple and scalable technique for the fabrication of solution processed & local gated carbon nanotube field effect transistors (CNT-FETs). The approach is based on directed assembly of individual single wall carbon nanotube from dichloroethane via AC dielectrophoresis (DEP) onto pre-patterned source and drain electrodes with a local aluminum gate in the middle. Local-gated CNT-FET devices display superior performance compared to global back gate with on-off ratios 10^4 and maximu...

  7. Hydrogel Actuation by Electric Field Driven Effects

    Morales, Daniel Humphrey

    Hydrogels are networks of crosslinked, hydrophilic polymers capable of absorbing and releasing large amounts of water while maintaining their structural integrity. Polyelectrolyte hydrogels are a subset of hydrogels that contain ionizable moieties, which render the network sensitive to the pH and the ionic strength of the media and provide mobile counterions, which impart conductivity. These networks are part of a class of "smart" material systems that can sense and adjust their shape in response to the external environment. Hence, the ability to program and modulate hydrogel shape change has great potential for novel biomaterial and soft robotics applications. We utilized electric field driven effects to manipulate the interaction of ions within polyelectrolyte hydrogels in order to induce controlled deformation and patterning. Additionally, electric fields can be used to promote the interactions of separate gel networks, as modular components, and particle assemblies within gel networks to develop new types of soft composite systems. First, we present and analyze a walking gel actuator comprised of cationic and anionic gel legs attached by electric field-promoted polyion complexation. We characterize the electro-osmotic response of the hydrogels as a function of charge density and external salt concentration. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices in aqueous solutions. An 'ionoprinting' technique is presented with the capability to topographically structure and actuate hydrated gels in two and three dimensions by locally patterning ions induced by electric fields. The bound charges change the local mechanical properties of the gel to induce relief patterns and evoke localized stress, causing rapid folding in air. The ionically patterned hydrogels exhibit programmable temporal and spatial shape transitions which can be tuned by the duration and/or strength of

  8. Electric field-free gas breakdown in explosively driven generators

    All known types of gas discharges require an electric field to initiate them. We are reporting on a unique type of gas breakdown in explosively driven generators that does not require an electric field.

  9. Radial-Electric-Field Piezoelectric Diaphragm Pumps

    Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma

    2009-01-01

    In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.

  10. Inductive heat property of Fe3O4 nanoparticles in AC magnetic field for local hyperthermia

    ZHAO Donglin; ZENG Xianwei; XIA Qisheng; TANG Jintian

    2006-01-01

    Magnetite (Fe3O4) nanoparticles with different magnetic properties were prepared by coprecipitation of Fe3+ and Fe2+ with aqueous NaOH solution.The inductive heat properties of Fe3O4 nanoparticles in an alternating current (AC) magnetic field were investigated for local hyperthermia. The maximum saunder the optimum conditions of Fe3+:Fe2+ molar ratio at 1.8:1. The Ms of Fe3O4 nanoparticles decreased as the Fe3+ /Fe2+ molar ratio increased. But the coercivity Hc increases with the increasing of Fe3+ /Fe2+ molar ratio. Exposed in the AC magnetic field for 29 min, the temperatures of physiological saline suspension containing Fe3O4 nanoparticles were 42-97.5 ℃.The inductive heat property of Fe3O4 nanoparticles in AC magnetic field decreases as Hc increases, but increases with the increasing of Ms. The Fe3O4 nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers.

  11. Theoretical study of electromagnetic electron cyclotron waves in the presence of AC field in Uranian magnetosphere

    Pandey, R. S.; Kaur, Rajbir

    2015-10-01

    Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit non-Maxwellian high-energy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electron-cyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.

  12. Electrostatic air filters generated by electric fields

    This paper presents theoretical and experimental findings on fibrous filters converted to electrostatic operation by a nonionizing electric field. Compared to a conventional fibrous filter, the electrostatic filter has a higher efficiency and a longer, useful life. The increased efficiency is attributed to a time independent attraction between polarized fibers and charged, polarized particles and a time dependent attraction between charged fibers and charged, polarized particles. The charge on the fibers results from a dynamic process of charge accumulation due to the particle deposits and a charge dissipation due to the fiber conductivity

  13. Perturbative renormalization of the electric field correlator

    Christensen, C.; Laine, M.

    2016-04-01

    The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ∼ 12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.

  14. Perturbative renormalization of the electric field correlator

    C. Christensen

    2016-04-01

    Full Text Available The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3 gauge theory, finding a ∼12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.

  15. Perturbative renormalization of the electric field correlator

    Christensen, C

    2016-01-01

    The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ~12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.

  16. Application of Pulsed Electric Field on Bacteria

    Kadlec, Tomáš; Babický, Václav; Člupek, Martin; Vrbová, M.

    Prague: Czech Technical University in Prague, 2011 - (Pospíšilová, M.; Vrbová, M.; Macháň, R.), s. 161-164 ISBN 978-80-01-04915-0. [Instruments and Methods for Biology and Medicine 2011. Kladno (CZ), 02.06.2011-02.06.2011] R&D Projects: GA AV ČR IAAX00430802; GA ČR(CZ) GD104/09/H080 Institutional research plan: CEZ:AV0Z20430508 Keywords : Pulsed Electric Field * Bacteria Subject RIV: BO - Biophysics

  17. Reversal of magnetization of a single-domain magnetic particle by the ac field of time-dependent frequency

    Cai, Liufei; Garanin, D.A.; Chudnovsky, E. M.

    2012-01-01

    We report numerical and analytical studies of the reversal of the magnetic moment of a single-domain magnetic particle by a circularly polarized ac field of time-dependent frequency. For the time-linear frequency sweep, the phase diagrams are computed that illustrate the dependence of the reversal on the frequency sweep rate v, the amplitude of the ac field h, the magnetic anisotropy field d, and the damping parameter alpha. It is shown that the most efficient magnetization reversal requires ...

  18. Predictive control of ac electric Arc furnace and its stability analysis

    An active power filter with dynamic control method is used for harmonic elimination and power factor correction of an Electric Arc Furnace. This new control technique is very suitable for suppressing harmonics of nonlinear loads. In addition, other parameters such as the power factor can also be controlled. A nonlinear model of Electric Arc Furnace and its Box-Jenkins model are used and compared. These models are parameterized by actual field data. The stability of the entire system is analyzed by using Stable Equilibrium Area Existencelemma

  19. Phosphate vibrations probe local electric fields and hydration in biomolecules

    Nicholas M Levinson; Bolte, Erin E.; Miller, Carrie S.; Corcelli, Steven A.; Boxer, Steven G.

    2011-01-01

    The role of electric fields in important biological processes like binding and catalysis has been studied almost exclusively by computational methods. Experimental measurements of the local electric field in macromolecules are possible using suitably calibrated vibrational probes. Here we demonstrate that the vibrational transitions of phosphate groups are highly sensitive to an electric field and quantify that sensitivity, allowing local electric field measurements to be made in phosphate-co...

  20. Phosphate vibrations probe local electric fields and hydration in biomolecules

    Levinson, Nicholas M.; Bolte, Erin E.; Miller, Carrie S.

    2011-01-01

    The role of electric fields in important biological processes like binding and catalysis has been studied almost exclusively by computational methods. Experimental measurements of the local electric field in macromolecules are possible using suitably calibrated vibrational probes. Here we demonstrate that the vibrational transitions of phosphate groups are highly sensitive to an electric field and quantify that sensitivity, allowing local electric field measurements to be made in phosphate-containing biological systems without chemical modification. PMID:21809829

  1. Characterization of composite particles responsive to electric and magnetic fields

    ZHAO Xiaopeng; GUO Hongxia

    2004-01-01

    The multilayer particles with responses to electric and magnetic fields are a prerequisite for particles assembled under external fields. Three routes to produce particles responsive to electric and magnetic fields are presented in this article. The size and morphology, properties as well as the electric-magnetic responses of three kinds of particles are comparatively discussed. This will provide a useful basis for the control of the behavior of the particles in suspensions by external electric and magnetic fields.

  2. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied

  3. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements

    Chérigier-Kovacic, L.; Ström, P.; Lejeune, A.; Doveil, F.

    2015-06-01

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

  4. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements

    Chérigier-Kovacic, L., E-mail: laurence.kovacic@univ-amu.fr; Doveil, F., E-mail: fabrice.doveil@univ-amu.fr [Aix-Marseille Université, CNRS, PIIM UMR 7345, FR-13397 Marseille Cedex 20 (France); Ström, P., E-mail: pestro@kth.se [Department of Fusion Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, 100 44 Stockholm (Sweden); Lejeune, A., E-mail: aurelien.lejeune@ametek.com [CAMECA SAS - 29 Quai des Grésillons, 92622 Gennevilliers Cedex (France)

    2015-06-15

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

  5. Brownian dipole rotator in alternating electric field

    Rozenbaum, V. M.; Vovchenko, O. Ye.; Korochkova, T. Ye.

    2008-06-01

    The study addresses the azimuthal jumping motion of an adsorbed polar molecule in a periodic n -well potential under the action of an external alternating electric field. Starting from the perturbation theory of the Pauli equation with respect to the weak field intensity, explicit analytical expressions have been derived for the time dependence of the average dipole moment as well as the frequency dependences of polarizability and the average angular velocity, the three quantities exhibiting conspicuous stochastic resonance. As shown, unidirectional rotation can arise only provided simultaneous modulation of the minima and maxima of the potential by an external alternating field. For a symmetric potential of hindered rotation, the average angular velocity, if calculated by the second-order perturbation theory with respect to the field intensity, has a nonzero value only at n=2 , i.e., when two azimuthal wells specify a selected axis in the system. Particular consideration is given to the effect caused by the asymmetry of the two-well potential on the dielectric loss spectrum and other Brownian motion parameters. When the asymmetric potential in a system of dipole rotators arises from the average local fields induced by an orientational phase transition, the characteristics concerned show certain peculiarities which enable detection of the phase transition and determination of its parameters.

  6. Brownian dipole rotator in alternating electric field.

    Rozenbaum, V M; Vovchenko, O Ye; Korochkova, T Ye

    2008-06-01

    The study addresses the azimuthal jumping motion of an adsorbed polar molecule in a periodic n -well potential under the action of an external alternating electric field. Starting from the perturbation theory of the Pauli equation with respect to the weak field intensity, explicit analytical expressions have been derived for the time dependence of the average dipole moment as well as the frequency dependences of polarizability and the average angular velocity, the three quantities exhibiting conspicuous stochastic resonance. As shown, unidirectional rotation can arise only provided simultaneous modulation of the minima and maxima of the potential by an external alternating field. For a symmetric potential of hindered rotation, the average angular velocity, if calculated by the second-order perturbation theory with respect to the field intensity, has a nonzero value only at n=2 , i.e., when two azimuthal wells specify a selected axis in the system. Particular consideration is given to the effect caused by the asymmetry of the two-well potential on the dielectric loss spectrum and other Brownian motion parameters. When the asymmetric potential in a system of dipole rotators arises from the average local fields induced by an orientational phase transition, the characteristics concerned show certain peculiarities which enable detection of the phase transition and determination of its parameters. PMID:18643221

  7. Electric field control of Skyrmions in magnetic nanodisks

    Nakatani, Y.; Hayashi, M.; Kanai, S.; Fukami, S.; Ohno, H.

    2016-04-01

    The control of magnetic Skyrmions confined in a nanometer scale disk using electric field pulses is studied by micromagnetic simulation. A stable Skyrmion can be created and annihilated by an electric field pulse depending on the polarity of the electric field. Moreover, the core direction of the Skyrmion can be switched using the same electric field pulses. Such creation and annihilation of Skyrmions, and its core switching do not require any magnetic field and precise control of the pulse length. This unconventional manipulation of magnetic texture using electric field pulses allows a robust way of controlling magnetic Skyrmions in nanodiscs, a path toward building ultralow power memory devices.

  8. Soil Identification using Field Electrical Resistivity Method

    Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.

    2015-06-01

    Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 Ωm & 285 Ωm) was slightly higher than SiltySAND (223 Ωm & 199 Ωm) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.

  9. Empirical high-latitude electric field models

    Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn-dusk OGO 6 measurements (J.P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the Y component of the interplanetary magnetic field. The objective, which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns, is met by deriving one pattern (model BC) for the northern hemisphere with a +Y interplanetary magnetic field (IMF) and southern hemisphere with a -Y IMF and two patterns (models A and DE) for the northern hemisphere with a -Y IMF and southern hemisphere with a +Y IMF. The most significant large-scale revisions of the OGO 6 models are (1) on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the IMF Y component, (2) on the nightside where a westward flow region poleward from the Harang discontinuity appears under model BC conditions, and (3) magnetic local time shifts in the positions of the convection cell foci. The modeling above was followed by a detailed examination of cases where the IMF Z component was clearly positive (northward). Neglecting the seasonally dependent cases where irregularities obscure pattern recognition, the observations range from reasonable agreement with the new BC and DE models, to cases where different characteristics appeared primarily at dayside high latitudes

  10. Electric-field-driven Phenomena for Manipulating Particles in Micro-Devices

    Khusid, Boris; Acrivos, Andreas

    2004-01-01

    Compared to other available methods, ac dielectrophoresis is particularly well-suited for the manipulation of minute particles in micro- and nano-fluidics. The essential advantage of this technique is that an ac field at a sufficiently high frequency suppresses unwanted electric effects in a liquid. To date very little has been achieved towards understanding the micro-scale field-and shear driven behavior of a suspension in that, the concepts currently favored for the design and operation of dielectrophoretic micro-devices adopt the approach used for macro-scale electric filters. This strategy considers the trend of the field-induced particle motions by computing the spatial distribution of the field strength over a channel as if it were filled only with a liquid and then evaluating the direction of the dielectrophoretic force, exerted on a single particle placed in the liquid. However, the exposure of suspended particles to a field generates not only the dielectrophoretic force acting on each of these particles, but also the dipolar interactions of the particles due to their polarization. Furthermore, the field-driven motion of the particles is accompanied by their hydrodynamic interactions. We present the results of our experimental and theoretical studies which indicate that, under certain conditions, these long-range electrical and hydrodynamic interparticle interactions drastically affect the suspension behavior in a micro-channel due to its small dimensions.

  11. Electric field assisted sintering (EFAST): Plasma?

    Electric Field Assisted Sintering (EFAST) discovered in third decade of nineteenth century. This field assisted sintering (FAST) plays a key role in compacting Nano-composites. This sintering technique is also named as Plasma Assisted Sintering (PAS). Commercially this technique is named as Spark Plasma Sintering (SPS). Plasma discharge plays a major role in consolidation of composites. The electrical discharge between powder particles results in confined to a small area and short-lived heating of the particles surfaces up to more than a few thousand degrees Celsius. Since the micro-plasma discharges form uniformly all through the sample volume, the generated heat is also consistently distributed. The particles surfaces are purified and activated due to the elevated temperature causing vaporization of the impurities strenuous on the particle surface. The purified surface layers of the particles melt and mingle to each other forming 'necks' between the particles. Several modeling and experimental studies carried out by researchers, but nobody confirms absolutely the existence of plasma in this technique till today. Present revise focusing on survival of PLASMA in Plasma Assisted Sintering (PAS) and its necessity. (author)

  12. Planned waveguide electric field breakdown studies

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  13. Tools and Setups for Experiments with AC and Rotating Magnetic Fields

    Ponikvar, D.

    2010-01-01

    A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several…

  14. Spin superconductivity and ac-Josephson effect in Graphene system under strong magnetic field

    Liu, Haiwen; Jiang, Hua; Sun, Qing-Feng; Xie, X. C.; Collaborative Innovation Center of Quantum Matter, Beijing, China Collaboration

    We study the spin superconductivity in Graphene system under strong magnetic field. From the microscopically Gor'kov method combined with the Aharonov-Casher effect, we derive the effective Landau-Ginzburg free energy and analyze the time evolution of order parameter, which is confirmed to be the off-diagonal long range order. Meanwhile, we compare the ground state of spin superconductivity to the canted-antiferromagnetic state, and demonstrate the equivalence between these two states. Moreover, we give out the pseudo-field flux quantization condition of spin supercurrent, and propose an experimental measurable ac-Josephson effect of spin superconductivity in this system.

  15. Comparison between critical current density in thin superconducting films estimated from temperature and field dependence of ac susceptibility

    Janů, Zdeněk, E-mail: janu@fzu.cz; Soukup, František

    2014-06-15

    Highlights: • ac magnetic susceptibility of thin film superconducting squares was measured. • Measurements were done as a function of the ac field amplitude or temperature. • Both data are well described on the basis of the Clem–Sanchez model. • We are able to interpret the whole behavior of the complex ac susceptibility. • The critical current and its temperature dependence are determined contact-less. - Abstract: We have measured an ac magnetic susceptibility of recent second generation high temperature superconductor wires (coated conductor tapes) both as a function of an amplitude of an applied ac magnetic field at fixed temperatures and as a function of temperature at the fixed amplitudes. We find that data acquired by both methods are well described by ac susceptibility calculated on the basis of the Clem–Sanchez model to a response of thin superconducting disks in the Bean critical state to an applied perpendicular ac magnetic field. We show how to link the empirical data dependent on the field amplitude or temperature with theoretical data dependent on the ratio between the critical current density and field amplitude. The critical depinning current densities and its temperature dependence found by both methods are in good agreement. We discuss and compare accuracy and time saving of both methods.

  16. Comparison between critical current density in thin superconducting films estimated from temperature and field dependence of ac susceptibility

    Highlights: • ac magnetic susceptibility of thin film superconducting squares was measured. • Measurements were done as a function of the ac field amplitude or temperature. • Both data are well described on the basis of the Clem–Sanchez model. • We are able to interpret the whole behavior of the complex ac susceptibility. • The critical current and its temperature dependence are determined contact-less. - Abstract: We have measured an ac magnetic susceptibility of recent second generation high temperature superconductor wires (coated conductor tapes) both as a function of an amplitude of an applied ac magnetic field at fixed temperatures and as a function of temperature at the fixed amplitudes. We find that data acquired by both methods are well described by ac susceptibility calculated on the basis of the Clem–Sanchez model to a response of thin superconducting disks in the Bean critical state to an applied perpendicular ac magnetic field. We show how to link the empirical data dependent on the field amplitude or temperature with theoretical data dependent on the ratio between the critical current density and field amplitude. The critical depinning current densities and its temperature dependence found by both methods are in good agreement. We discuss and compare accuracy and time saving of both methods

  17. Electric field sensing: What is brought by duality from flux gates?

    Robbes, Didier; Jorel, Corentin; Olivier, E.; Mechin, Laurence; Lebargy, Sylvain; Bouregba, Rachid; Poullain, Gilles; Cibert, C

    2013-01-01

    International audience Ways to sense electric field using PZT capacitors are investigated. Duality rules a priori apply to material physics, linking polarization to magnetization properties, i.e. D(E) to B(H) curves, but no real electrical flux gate or charge gate does exist which would be the dual of the common flux gate magnetometer. The Landau - Khalatnikov equations are applied to ferroelectric materials subjected to both a DC and an AC pumping signal. They are solved to get the model ...

  18. Hypersensitivity test to electric magnetic fields

    The so-called electromagnetic hypersensitivity (RH) syndrome includes a number of unspecific, medically unexplained symptoms attributed to exposure to electric and magnetic fields. As a whole, laboratory tests have provided inconclusive results, in part due to the fact that many individuals show nuclear, inconsistent responses to repeated experimental field-exposures. It has been proposed that such inconsistencies could be due in part to distress caused by the lab test itself. We have developed a test to be conducted at the patient's residence, allowing for long-term follow up of exposure-response assessment and avoiding the laboratory environment and the presence of the researcher as potential stressors and confounding factors. In a pilot test, EMDEX-II magnetometers were used to continuously recording power-frequency magnetic fields in the residence of a patient with perceived EH. The patient's symptoms included distress, headache and dizziness, among other ailments. Magnetographic data of a total of 123 recording days were plotted against the corresponding data on occurrence of the symptoms episodes. As a whole, the results did not show positive linear correlation between the daily occurrence of the episode and the exposures levels recorded during the day or during the day before. These preliminary results are little supportive of the hypothesis that the patient's ailments are caused or worsened by a putative hypersensitivity to residential exposure to power-frequency magnetic fields in the 0.02-4.00 μT range. (Author) 29 refs

  19. Dynamic melting and impurity particle tracking in continuously adjustable AC magnetic field

    Bojarevics, V.; Pericleous, K.

    2016-07-01

    The analysis of semi-levitation melting is extended to account for the presence of particles (impurities, broken metal dendrite agglomerates, bubbles) during the full melting cycle simulated numerically using the pseudo-spectral schemes. The AC coil is dynamically moving with the melt front progress, while the generated Joule heat serves to enhance the melting rate. The electromagnetic force is decomposed into the time average and the oscillating parts. The time average effects on the particle transport are investigated previously using approximations derived for a locally uniform magnetic field. This paper presents expressions for the skin-layer type of the AC force containing also the pulsating part which contributes to the particle drag by the ‘history’ and ‘added mass’ contributions. The intense turbulence in the bulk of molten metal additionally contributes to the particle dispersion. The paper attempts to demonstrate the importance of each of the mentioned effects onto the particle transport during the melting until the final pouring stage. The method could be extended to similar AC field controlled melting/solidification processes.

  20. Magnetic resonance electrical impedance tomography for determining electric field distribution during electroporation

    Electroporation is a phenomenon caused by externally applied electric field to cells that results in an increase of cell membrane permeability to various molecules. Accurate coverage of the tissue with a sufficiently large electric field presents one of the most important conditions for successful membrane permeabilization. Applications based on electroporation would greatly benefit with a method for monitoring the electric field, especially if it could be done in situ. As the membrane electroporation is a consequence of an induced transmembrane potential, which is directly proportional to the local electric field, we have been investigating current density imaging and magnetic resonance electrical impedance tomography techniques to determine the electric field distribution during electroporation. In this paper, we present comparison of current density and electric field distribution in an agar phantom and in a liver tissue exposed to electroporation pulses. As expected, a region of increased electrical conductivity was observed in the liver tissue exposed to sufficiently high electric field but not in agar phantom.

  1. Anisotropy of magnetic emulsions induced by magnetic and electric fields

    Dikansky, Yury I.; Tyatyushkin, Alexander N.; Zakinyan, Arthur R.

    2011-01-01

    The anisotropy of magnetic emulsions induced by simultaneously acting electric and magnetic fields is theoretically and experimentally investigated. Due to the anisotropy, the electric conductivity and magnetic permeability of a magnetic emulsion are no longer scalar coefficients, but are tensors. The electric conductivity and magnetic permeability tensors of sufficiently diluted emulsions in sufficiently weak electric and magnetic fields are found as functions of the electric and magnetic in...

  2. Experimental Investigation of Integrated Optical Intensive Impulse Electric Field Sensors

    We design and fabricate an integrated optical electric field sensor with segmented electrode for intensive impulse electric field measurement. The integrated optical sensor is based on a Mach–Zehnder interferometer with segmented electrodes. The output/input character of the sensing system is analysed and measured. The maximal detectable electric field range (−75 kV/m to 245 kV/m) is obtained by analysing the results. As a result, the integrated optics electric field sensing system is suitable for transient intensive electric field measurement investigation

  3. Inhibition of brain tumor cell proliferation by alternating electric fields

    Jeong, Hyesun; Oh, Seung-ick; Hong, Sunghoi, E-mail: shong21@korea.ac.kr, E-mail: radioyoon@korea.ac.kr [School of Biosystem and Biomedical Science, Korea University, Seoul 136-703 (Korea, Republic of); Sung, Jiwon; Jeong, Seonghoon; Yoon, Myonggeun, E-mail: shong21@korea.ac.kr, E-mail: radioyoon@korea.ac.kr [Department of Bio-convergence Engineering, Korea University, Seoul 136-703 (Korea, Republic of); Koh, Eui Kwan [Seoul Center, Korea Basic Science Institute, Seoul 136-713 (Korea, Republic of)

    2014-11-17

    This study was designed to investigate the mechanism by which electric fields affect cell function, and to determine the optimal conditions for electric field inhibition of cancer cell proliferation. Low-intensity (<2 V/cm) and intermediate-frequency (100–300 kHz) alternating electric fields were applied to glioblastoma cell lines. These electric fields inhibited cell proliferation by inducing cell cycle arrest and abnormal mitosis due to the malformation of microtubules. These effects were significantly dependent on the intensity and frequency of applied electric fields.

  4. Experimental Investigation of Integrated Optical Intensive Impulse Electric Field Sensors

    SUN Bao; CHEN Fu-Shen

    2009-01-01

    We design and fabricate an integrated optical electric field sensor with segmented electrode for intensive im-pulse electric field measurement. The integrated optical sensor is based on a Mach-Zehnder interferometer with segmented electrodes. The output/input character of the sensing system is analysed and measured. The max-imal detectable electric field range (-75 kV/m to 245 kV/m) is obtained by analysing the results. As a result, the integrated optics electric field sensing system is suitable for transient intensive electric field measurement investigation.

  5. Inhibition of brain tumor cell proliferation by alternating electric fields

    This study was designed to investigate the mechanism by which electric fields affect cell function, and to determine the optimal conditions for electric field inhibition of cancer cell proliferation. Low-intensity (<2 V/cm) and intermediate-frequency (100–300 kHz) alternating electric fields were applied to glioblastoma cell lines. These electric fields inhibited cell proliferation by inducing cell cycle arrest and abnormal mitosis due to the malformation of microtubules. These effects were significantly dependent on the intensity and frequency of applied electric fields

  6. Saturation of the Electric Field Transmitted to the Magnetosphere

    Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James A.

    2010-01-01

    We reexamined the processes leading to saturation of the electric field, transmitted into the Earth's ionosphere from the solar wind, incorporating features of the coupled system previously ignored. We took into account that the electric field is transmitted into the ionosphere through a region of open field lines, and that the ionospheric conductivity in the polar cap and auroral zone may be different. Penetration of the electric field into the magnetosphere is linked with the generation of the Alfven wave, going out from the ionosphere into the solar wind and being coupled with the field-aligned currents at the boundary of the open field limes. The electric field of the outgoing Alfven wave reduces the original electric field and provides the saturation effect in the electric field and currents during strong geomagnetic disturbances, associated with increasing ionospheric conductivity. The electric field and field-aligned currents of this Alfven wave are dependent on the ionospheric and solar wind parameters and may significantly affect the electric field and field-aligned currents, generated in the polar ionosphere. Estimating the magnitude of the saturation effect in the electric field and field-aligned currents allows us to improve the correlation between solar wind parameters and resulting disturbances in the Earth's magnetosphere.

  7. Calculation of Electric Field Characteristics of Insulator Under Sandstorm Condition

    Zhao Shanpeng; Zhang Youpeng; Chen Zhidong; Dong Haiyan

    2013-01-01

    Sandstorm has influence on the the electrical properties of outdoor insulator, and the analysis of the electric field characteristics of insulator under sandstorm condition is very important. The electrostatic field finite element method (FEM) is used to calculate the electric field distribution along long rod insulator under sandstorm condition with FEM software after calculating the one under clean condition. The results of calculation show that the sand deposition decreases the electric fi...

  8. Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment

    Silenko, A. J.

    2013-01-01

    A buildup of the vertical polarization in the resonant electric dipole moment (EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev. Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the particle rest frame oscillating at a resonant frequency. This field is defined by the Lorentz transformation of an oscillating longitudinal electric field and a uniform vertical magnetic one. The effect of a longitudinal electric field is significant, while the cont...

  9. Aligned Single Wall Carbon Nanotube Polymer Composites Using an Electric Field

    Park, Cheol; Wiklinson, John; Banda, Sumanth; Ounaies, Zoubeida; Wise, Kristopher E.; Sauti, Godfrey; Lillehei, Peter T.; Harrison, Joycelyn S.

    2005-01-01

    While high shear alignment has been shown to improve the mechanical properties of single wall carbon nanotubes (SWNT)-polymer composites, it is difficult to control and often results in degradation of the electrical and dielectric properties of the composite. Here, we report a novel method to actively align SWNTs in a polymer matrix, which allows for control over the degree of alignment of SWNTs without the side effects of shear alignment. In this process, SWNTs are aligned via field-induced dipolar interactions among the nanotubes under an AC electric field in a liquid matrix followed by immobilization by photopolymerization while maintaining the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy and the morphology of the aligned nanocomposites was investigated by high resolution scanning electron microscopy. The structure of the field induced aligned SWNTs is intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties in addition to improving the mechanical properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field conditions.

  10. MTX microwave-electric-field diagnostic

    A joint Japan-U.S. project is in progress to measure the high electric fields produced by a free-electron laser beam of GW-peak-power level when injected into the plasma of the Microwave Tokamak Experiment (MTX) at the Lawrence Livermore National Laboratory in California. In this report, we discuss the planned method of measurement and the status of the work. The equipment needed is either well along in the design stage or is being built. We plan to test out the combined operation of all components in Japan before shipping to Livermore. Although the measurement appears difficult for a variety of technical and physics reasons, calculations indicate that it should be possible. (author)

  11. AC susceptibility of Sr2RuO4-Sr3Ru2O7 eutectics: Dependence on AC field strength and frequency

    The low-field AC susceptibility of a eutectic crystal of the Sr2RuO4-Sr3Ru2O7 system exhibits superconducting transition features at three temperatures. We investigate the dependence on AC field strength from 0.021 to 2.1 Oe-rms and frequency from 17 to 3 kHz. The two lower-temperature peaks in the imaginary part originate in the Sr3Ru2O7 part. The lowest-temperature peak is exceedingly sensitive to the field amplitude and shifts to lower temperatures with increasing amplitude. By contrast, it slightly shifts to higher temperatures with increasing frequency. These results support that the sensitive features involve weak links forming the screening paths

  12. Electrical integrity of oxides in a radiation field

    Zinkle, S.J. [Oak Ridge National Laboratory, TN (United States); Kinoshita, C.

    1996-04-01

    In the absence of an applied electric field, irradiation generally produces a decrease in the permanent (beam-off) electrical conductivity of ceramic insulators. However, in the past 6 years several research groups have reported a phenomenon known as radiation induced electrical degradation (RIED), which produces significant permanent increases in the electrical conductivity of ceramic insulators irradiated with an applied electric field. RIED has been reported to occur at temperatures between 420 and 800 K with applied electric fields as low as 20 V/mm.

  13. Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0.5Na0.50.95Ba0.05TiO3 ceramic

    Ansu K. Roy

    2013-06-01

    Full Text Available Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.50.95Ba0.05TiO3 (BNT-BT0.05, prepared by conventional high temperature solid state reaction technique at 1160 °C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35–400 °C, over a frequency range 100 Hz–1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80 °C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analysed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM were found to explain successfully the mechanism of charge transport in BNT-BT0.05.

  14. Electric field control of spin dynamics in a magnetically active tunnel junction

    The dynamics of a single spin embedded in a tunnelling junction is studied. Within a nonequilibrium Keldysh Green's function technique, we derive a quantum Langevin equation describing the spin dynamics. In the high temperature limit, it reduces to a Bloch equation, for which the spin relaxation rate, as determined by the temporal fluctuation, is linearly proportional to the temperature. In the opposite limit, the relaxation rate depends on the applied voltage, in contrast to the case of a spin in an equilibrium environment. We also show that spin-flip transition processes during electron tunnelling convert the applied electric field (i.e. voltage bias) into an effective magnetic field. Consequently, the dynamics of the spin, otherwise precessing along the static magnetic field, will have either a frequency shift proportional to the dc bias or a magnetic resonance driven indirectly by an ac electric field at the Larmor frequency ωL. An experiment to measure this effect is also proposed

  15. Electric field-dependent dynamic polarizability and "magic'' conditions for optical trapping of polar molecules

    Kotochigova, Svetlana

    2010-01-01

    Selection of ``magic'' trapping conditions with ultracold atoms or molecules, where pairs of internal states experience identical trapping potentials, brings substantial benefits to precision measurements and quantum computing schemes. Working at such conditions could ensure that detrimental effects of inevitable inhomogeneities across an ultracold sample are significantly reduced. However, this aspect of confinement remains unexplored for ultracold polar molecules. Here, we present means to control the AC Stark shift of rotational states of ultracold polar molecules, when subjected to both trapping laser light and an external electric field. We show that both the strength and relative orientation of the two fields influence the trapping potential. In particular, we predict ``magic electric field strengths" and a ``magic angle", where the Stark shift is independent of the DC external field and rotational states of the molecule.

  16. Difficulties in Learning the Concept of Electric Field.

    Furio, C.; Guisasola, J.

    1998-01-01

    Analyzes students' main difficulties in learning the concept of electric field. Briefly describes the main conceptual profiles within which electric interactions can be interpreted and concludes that most students have difficulty using the idea of electric field. Contains 28 references. (DDR)

  17. Development of an electric power conversion system using a high frequency AC insulating link system. Koshuha AC zetsuen link hoshiki wo mochiita denryoku henkan system no kaihatsu

    1991-05-10

    An electric power convertion system incorporating a cycloconverter type high frequency AC insulating link system of which object was the dispersed power sources of 5KVA class was experimentally developed to evaluate the properties of the developed equipment. The system was composed of a cycloconverter which converted the frequency from 20kHz to 60Hz directly by converting DC to high frequency AC at the 20kHz high frequency inverter, and then by connecting to a high frequency transformer which insulated between the inputting side and the outputting circuit. The multi-functional hybrid IC technology where semiconductor elements, driving circuits, current detecting elements and overcurrent cut-off circuits were incorporated into a module, was introduced. As a result, the size of the high frequency transformer became one-tenth or less the size of transformer using commercial frequency and the weight reduced to about one-twentyfifth. When the commutation of high frequency power source and the forced gate commutation were used jointly, the efficiency was improved by 10 percentage at the 100 percentage load, compared with the case using only the forced gate commutation and the efficiency of mounted equipment was 90 percentage. 3 figs.

  18. Self-field ac losses in biaxially aligned Y endash Ba endash Cu endash O tape conductors

    Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y endash Ba endash Cu endash O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high Jc sample, and agreed well with Norris close-quote equation for thin strip conductors. However, the low Jc sample had rather higher losses than Norris close-quote prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris close-quote prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors. copyright 1997 American Institute of Physics

  19. Silica microwire-based interferometric electric field sensor.

    Han, Chunyang; Lv, Fangxing; Sun, Chen; Ding, Hui

    2015-08-15

    Silica microwire, as an optical waveguide whose diameter is close to or smaller than the wavelength of the guided light, is of great interest because it exhibits a number of excellent properties such as tight confinement, large evanescent fields, and great configurability. Here, we report a silica microwire-based compact photonic sensor for real-time detection of high electric field. This device contains an interferometer with propylene carbonate cladding. Based on the Kerr electro-optic effect of propylene carbonate, the applied intensive transient electric field can change the refractive index of propylene carbonate, which shifts the interferometric fringe. Therefore, the electric field could be demodulated by monitoring the fringe shift. The sensor was successfully used to detect alternating electric field with frequency of 50 Hz and impulse electric field with duration time of 200 μs. This work lays a foundation for future applications in electric field sensing. PMID:26274634

  20. Calculation of Electric Field Characteristics of Insulator Under Sandstorm Condition

    Zhao Shanpeng

    2013-09-01

    Full Text Available Sandstorm has influence on the the electrical properties of outdoor insulator, and the analysis of the electric field characteristics of insulator under sandstorm condition is very important. The electrostatic field finite element method (FEM is used to calculate the electric field distribution along long rod insulator under sandstorm condition with FEM software after calculating the one under clean condition. The results of calculation show that the sand deposition decreases the electric field strength of insulator covered with sand, and increases the field strength of the corresponding shed key points. The electric field strength of the non-sand region will increase, when the non-sand region appears in sand layer on insulator. Suspended sand particles in the ambient air can distort the electric field distribution along insulator, and which is significantly affected by the size, the quantity, the charge-to-mass ratio and the charge polarity of sand particles.

  1. Shot noise in nano-electronic systems under the perturbation of ac fields

    ZHAO Hong-kang

    2007-01-01

    Current noise exists in circuits and electronic devices generally, and it exhibits specific features as the system reaches nanometer size. The noise in the nano-system where external ac fields are applied plays an important role, since the properties of the fields and the nano-system together govern the resulting noise. In this paper, we present the derivation of shot noise by employing the nonequilibrium Green's function technique. The more general formulas for the current correlation and noise spectral density are given. The system is composed of a central nanosystem coupled to electrodes, and the obtained noise formulas are related to the Green's functions of detailed central regime and the terminals. As an example, we have performed the numerical calculation on a system with a toroidal carbon nanotube coupled to normal metal leads. The noise and Fano factor show intimate relation with the structure of the system and ac fields. The Aharonov-Bohm-like behaviors on the shot noise spectral density and Fano factor are observed to exhibit oscillation structures with period of quantum flux.

  2. AC transport in p-Ge/GeSi quantum well in high magnetic fields

    Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.; Golub, L. E.; Tarasenko, S. A. [A.F. Ioffe Physical Technical Institute of Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Suslov, A. V. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Mironov, O. A. [Warwick SEMINANO R and D Center, University of Warwick Science Park, Coventry CV4 7EZ (United Kingdom); Kummer, M.; Känel, H. von [Laboratorium für Festkörperphysik ETH Zürich, CH-8093 Zürich (Switzerland)

    2014-08-20

    The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shown that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.

  3. Magnetic fluid hyperthermia (MFH): Cancer treatment with AC magnetic field induced excitation of biocompatible superparamagnetic nanoparticles

    Jordan, Andreas; Scholz, Regina; Wust, Peter; Fähling, Horst; Felix, Roland

    1999-07-01

    The story of hyperthermia with small particles in AC magnetic fields started in the late 1950s, but most of the studies were unfortunately conducted with inadequate animal systems, inexact thermometry and poor AC magnetic field parameters, so that any clinical implication was far behind the horizon. More than three decades later, it was found, that colloidal dispersions of superparamagnetic (subdomain) iron oxide nanoparticles exhibit an extraordinary specific absorption rate (SAR [ W/ g]), which is much higher at clinically tolerable H 0 f combinations in comparison to hysteresis heating of larger multidomain particles. This was the renaissance of a cancer treatment method, which has gained more and more attention in the last few years. Due to the increasing number of randomized clinical trials preferentially in Europe with conventional E-field hyperthermia systems, the general medical and physical experience in hyperthermia application is also rapidly growing. Taking this increasing clinical experience carefully into account together with the huge amount of new biological data on heat response of cells and tissues, the approach of magnetic fluid hyperthermia (MFH) is nowadays more promising than ever before. The present contribution reviews the current state of the art and some of the future perspectives supported by advanced methods of the so-called nanotechnology.

  4. Electric motors and drives. Pt. 27. AC motors. Pt. 1; Elektrische Maschinen und Antriebe. T. 27. Drehfeldmaschinen. T. 1

    Baral, Andreas [FHWT - Private Fachhochschule fuer Wirtschaft und Technik, Oldenburg (Germany). Elektrische Maschinen und Antriebstechnik

    2009-11-15

    AC motors like, for example, asynchronous and synchronous motors have an important role in propulsion technology. They are based on the principle of a rotary magnetic field resulting from the motor geometry and from a multiphase (usually three-phase) voltage system. The rotational frequency of the field and thus the rotary speed of the motors are directly dependent on the frequency of the feeding voltage system. (orig.)

  5. The investigation of an electric arc in the long cylindrical channel of the powerful high-voltage AC plasma torch

    The comparison of conductivity obtained in experiments with calculated values is made in this paper. Powerful stationary plasma torches with prolonged period of continuous work are popular for modern plasmachemical applications. The maximum electrode lifetime with the minimum erosion can be reached while working on rather low currents. Meanwhile it is required to provide voltage arc drop for the high power achievement. Electric field strength in the arc column of the high-voltage plasma torch, using air as a plasma-forming gas, does not exceed 15 V/cm. It is possible to obtain the high voltage drop in the long arc stabilized in the channel by the intensive gas flow under given conditions. Models of high voltage plasma torches with rod electrodes with power up to 50 kW have been developed and investigated. The plasma torch arcs are burning in cylindrical channels. Present investigations are directed at studying the possibility of developing long arc plasma torches with higher power. The advantage of AC power supplies usage is the possibility of the loss minimization due to the reactive power compensation. The theoretical maximum of voltage arc drop for power supplies with inductive current limitations is about 50 % of the no-load voltage for a single-phase circuit and about 30 % for the three-phase circuit. Burning of intensively blown arcs in the long cylindrical channel using the AC power supply with 10 kV no-load voltage is experimentally investigated in the work. Voltage drops close to the maximum possible had been reached in the examined arcs in single-phase and three-phase modes. Operating parameters for single-phase mode were: current −30 A, voltage drop −5 kV, air flow rate 35 g/s; for three-phase mode: current (40–85) A, voltage drop (2.5–3.2) kV, air flow rate (60–100) g/s. Arc length in the installations exceeded 2 m.

  6. Estimation of frequency-dependent electrokinetic forces on tin oxide nanobelts in low frequency electric fields

    Kumar, Surajit; Hesketh, Peter J, E-mail: surajitk@gatech.edu [George W Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

    2010-08-13

    A novel experimental approach is used for studying the response of ethanol-suspended SnO{sub 2} nanobelts under the influence of low frequency ac electric fields. The electrically generated forces are estimated by analyzing the angular motion of the nanobelt, induced by repulsive forces originating predominantly from negative dielectrophoresis (DEP) on planar microelectrodes. The nanobelt motion is experimentally recorded in real time in the low frequency range (<100 kHz) and the angular velocities are calculated. A simple analytical model of force balance between the electrical forces and fluidic drag for long nano-objects is developed and used to deduce estimates of the frequency-dependent DEP force and torque magnitudes from the angular velocity data. Additional experiments, performed in a parallel plate electrode configuration in a fluidic channel to investigate the effect of dc and very low frequency ac ({approx}Hz) electric fields, indicate the presence of electrophoresis in the ethanol-suspended SnO{sub 2} nanobelts. The experimentally observed nanobelt motion is analyzed using the equation of motion, and an order-of-magnitude estimate of the nanobelt surface charge density is obtained.

  7. Pair Creation of Open Strings in an Electric Field

    Bachas, C.; Porrati, M.

    1992-01-01

    We calculate exactly the rate of pair production of open bosonic and supersymmetric strings in a constant electric field. The rate agrees with Schwinger's classic result in the weak-field limit, but diverges when the electric field approaches some critical value of the order of the string tension. (Phyzzx file)

  8. Giant enhancement of photodissociation of polar dimers in electric fields

    González-Férez, R.; Schmelcher, P.

    2011-01-01

    We explore the photodissociation of polar dimers in static electric fields in the cold regime using the example of the LiCs molecule. A giant enhancement of the differential cross section is found for laboratory electric field strengths, and analyzed with varying rovibrational bound states, continuum energies as well as field strengths.

  9. Generation of Electric Field and Net Charge in Hall Reconnection

    MA Zhi-Wei; FENG Shu-Ling

    2008-01-01

    @@ Generation of Hall electric field and net charge associated with magnetic reconnection is studied under different initial conditions of plasma density and magnetic field. With inclusion of the Hall effects, decoupling of the electron and ion motions leads to the formation of a narrow layer with strong electric field and large net charge density along the separatrix. The asymmetry of the plasma density or magnetic field or both across the current sheet will largely increase the magnitude of the electric field and net charge. The results indicate that the asymmetry of the magnetic field is more effective in producing larger electric field and charge density. The electric field and net charge are always much larger in the low density or/and high magnetic field side than those in the high density or/and low magnetic field side. Both the electric field and net charge density are linearly dependent on the ratios of the plasma density or the square of the magnetic field across the current sheet. For the case with both initial asymmetries of the magnetic field and density, rather large Hall electric field and charge density are generated.

  10. Flow-Driven Cell Migration under External Electric Fields

    Li, Yizeng; Mori, Yoichiro; Sun, Sean X.

    2015-12-01

    Electric fields influence many aspects of cell physiology, including various forms of cell migration. Many cells are sensitive to electric fields, and they can migrate toward a cathode or an anode, depending on the cell type. In this Letter, we examine an actomyosin-independent mode of cell migration under electrical fields. Our theory considers a one-dimensional cell with water and ionic fluxes at the cell boundary. Water fluxes through the membrane are governed by the osmotic pressure difference across the cell membrane. Fluxes of cations and anions across the cell membrane are determined by the properties of the ion channels as well as the external electric field. Results show that without actin polymerization and myosin contraction, electric fields can also drive cell migration, even when the cell is not polarized. The direction of migration with respect to the electric field direction is influenced by the properties of ion channels, and are cell-type dependent.

  11. Computation of induced electric field for the sacral nerve activation

    Hirata, Akimasa; Hattori, Junya; Laakso, Ilkka; Takagi, Airi; Shimada, Takuo

    2013-11-01

    The induced electric field/current in the sacral nerve by stimulation devices for the treatment of bladder overactivity is investigated. Implanted and transcutaneous electrode configurations are considered. The electric field induced in the sacral nerve by the implanted electrode is largely affected by its surrounding tissues, which is attributable to the variation in the input impedance of the electrode. In contrast, the electric field induced by the transcutaneous electrode is affected by the tissue conductivity and anatomical composition of the body. In addition, the electric field induced in the subcutaneous fat in close proximity of the electrode is comparable with the estimated threshold electric field for pain. These computational findings explain the clinically observed weakness and side effect of each configuration. For the transcutaneous stimulator, we suggest that the electrode contact area be increased to reduce the induced electric field in the subcutaneous fat.

  12. Computation of induced electric field for the sacral nerve activation

    The induced electric field/current in the sacral nerve by stimulation devices for the treatment of bladder overactivity is investigated. Implanted and transcutaneous electrode configurations are considered. The electric field induced in the sacral nerve by the implanted electrode is largely affected by its surrounding tissues, which is attributable to the variation in the input impedance of the electrode. In contrast, the electric field induced by the transcutaneous electrode is affected by the tissue conductivity and anatomical composition of the body. In addition, the electric field induced in the subcutaneous fat in close proximity of the electrode is comparable with the estimated threshold electric field for pain. These computational findings explain the clinically observed weakness and side effect of each configuration. For the transcutaneous stimulator, we suggest that the electrode contact area be increased to reduce the induced electric field in the subcutaneous fat. (paper)

  13. Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons

    Iversen, I. B.; Madsen, M. M.; Dangelo, N.

    1985-01-01

    Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.

  14. Measurement of electric fields in the H-1NF heliac

    There are a number of laser induced fluorescence techniques which can be used to measure internal plasma electric fields. It is planned to use a technique based on Stark mixing of energy levels in a supersonic beam containing metastable helium atoms to measure radial electric fields in H-1NF. Enhanced values of radial electric field are associated with improved confinement modes in H-1NF and other magnetically confined plasmas

  15. The electric field gradient in fluorides

    The electric quadrupole hyperfine interaction was investigated for various fluorides by the time-differential observation of the perturbed γ angular correlation and the Kern-Hanle effect of the 197 keV radiation of the 5/2+ level in 19F. This level was excited by inelastic proton scattering. The dependence of the quadrupole coupling constant from the chemical bond of the atom to its ligands was measured in fluorides of two-valid transition elements and in pureley covalent molecules, as (CF2)sub(n) or SF6. The influence of radiation-induced defects in nonmetals was investigated for cubic fluorides between 80 K and 1050 K. For CaF2 two different field gradients are obtained with coupling constants between 27 MHz and 3 MHz. By measurements of the angular distribution for CaF2/PrF3 mixed crystals which contain a variable concentration of F- interstitials was shown that the appearance of the 3 MHz frequency is correlated with the concentration of F- interstitials in CaF2. (BHO)

  16. Electric field breakdown in single molecule junctions.

    Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2015-04-22

    Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085

  17. Substorm electric fields in the earth's magnetotail

    A survey has been made of all the electric field data from the University of California, Berkeley, double probe experiment on ISEE-1 (apogee approximately 22 earth radii) during 1980 when the satellite was in the magnetotail. This study was restricted to the 74 events where E cross B flows could be calculated and were equal to or greater than 100 km/s. Substorm times were determined by examining the Ae index for peaks equal to or greater than 250 gamma. In association with substorms, approximately 70 percent of the flows were earthward, and approximately 20 percent had a signature called near satellite reconnection (first described by Nishida et al. (1983) of tailward flow followed by earthward flow which can be interpreted in terms of a model where the x-line forms earthward of the satellite and subsequently propagates tailward of X(GSM) = -21 earth radii and within the absolute value of Y(GSM) equal to or less than 4.5 earth radii. These data suggest that the near earth x-line usually forms tailward of X(GSM) approximately -20 earth radii. 17 references

  18. Effect of increased ionization on the atmospheric electric field

    This study is a review of atmospheric electrical theory with the purpose of predicting the atmospheric electrical effects of increased ionization caused by radioactive inert gases. A time-independent perturbation model for the global atmospheric electric circuit precdicts that the electric field at the sea surface would be reduced to about 76% of its unperturbed value by a surface 85Kr concentration of 3 nCi/m3. The electric field at a typical land station is predicted to be about 84% of its unperturbed value. Some scientists have suggested that the atmospheric electric field is part of a closed electrical feedback loop. The present model does not include such a closed feedback loop and may underestimate the total effects. This model is also useful for interpreting atmospheric electrical responses to natural fluctuations in the cosmic-ray component of background radiation

  19. High electric field measurement using slab-coupled optical sensors.

    Stan, Nikola; Seng, Frederick; Shumway, LeGrand; King, Rex; Selfridge, Richard; Schultz, Stephen

    2016-01-20

    A fiber-optic electric field sensor was developed to measure electric field up to 18 MV/m. The sensor uses resonant coupling between an optical fiber and a nonlinear electro-optical crystal. The sensing system uses high dielectric strength materials to eliminate dielectric breakdown. A postprocessing nonlinear calibration method is developed that maps voltage change to wavelength shift and then converts the wavelength shift to electric field using the transmission spectrum. The nonlinear calibration method is compared against the linear method with electric field pulses having magnitudes from 1.5 to 18 MV/m. PMID:26835936

  20. Linear electric field time-of-flight ion mass spectrometer

    Funsten, Herbert O.; Feldman, William C.

    2008-06-10

    A linear electric field ion mass spectrometer having an evacuated enclosure with means for generating a linear electric field located in the evacuated enclosure and means for injecting a sample material into the linear electric field. A source of pulsed ionizing radiation injects ionizing radiation into the linear electric field to ionize atoms or molecules of the sample material, and timing means determine the time elapsed between ionization of atoms or molecules and arrival of an ion out of the ionized atoms or molecules at a predetermined position.

  1. Dynamics of carbon nanotube alignment by electric fields

    The dynamics of multiwall carbon nanotube (MWCNT) alignment inside viscous media using electric fields is investigated. Electrical current measurements were performed in situ during the application of an electric field to liquid solutions of deionized water or dissolved polymer containing MWCNTs. The variation of electrical current over time was associated to the dynamics of the MWCNT network formation. The influence of the electric field magnitude and frequency on the MWCNT network formation was studied. MWCNT migration towards the negative electrode was observed when a direct current electric field was applied, whereas formation of an aligned MWCNT network was achieved for an alternating current electric field. The increase of the electric field frequency promotes a faster formation of an aligned MWCNT network and thinner MWCNT bundles. A higher viscosity of the liquid medium yields slower MWCNT alignment evidenced by a slower change of electrical current through the viscous system. An analytical model based on the dielectrophoresis-induced torque, which considers the viscosity of the medium, is also proposed to explain the dynamics of MWCNT alignment. Furthermore, aligned MWCNT/polysulfone solid composites were fabricated and electrically characterized. The solid composites presented anisotropic electrical conductivity, which was more evident for low MWCNT concentrations (0.1–0.2 wt%). (paper)

  2. ac losses and field and current density distribution during a full cycle of a stack of superconducting tapes

    Yuan, Weijia; Campbell, A. M.; Coombs, T. A.

    2010-05-01

    Starting from an existing model by Clem et al., this paper has analyzed how the current density and magnetic field distribution of a stack of superconducting tapes with ac transport currents or applied fields will change in a full cycle. This paper assumes when the ac current or field starts to change in the other direction, a new penetrated region will begin to penetrate from the superconductor surface. If we assume Jc is constant in the critical region, this paper demonstrates that the Claassen formula (7) can be used to calculate the exact ac losses. If Jc depends on local Bz, we can use Eq. (9) to quickly predict the ac losses. This approach does not need to calculate a complete ac cycle. This saves considerably computation time while gives a result which is in close agreement with that calculated from a complete ac cycle. The calculation method can be applied for calculating a superconducting pancake coil if the coil radius is much larger than the tape width.

  3. Electric Field Effects in Self-Propagating High-Temperature Synthesis under Microgravity Conditions

    Unuvar, C.; Frederick, D. M.; Shaw, B. D.; Munir, Z. A.

    2003-01-01

    Self-propagating high-temperature synthesis (SHS) has been used to form many materials. SHS generally involves mixing reactants together (e.g., metal powders) and igniting the mixture such that a combustion (deflagration) wave passes though the mixture. The imposition of an electric field (AC or DC) across SHS reactants has been shown to have a marked effect on the dynamics of wave propagation and on the nature, composition, and homogeneity of the product . The use of an electric field with SHS has been termed "field-assisted SHS". Combustion wave velocities and temperatures are directly affected by the field, which is typically perpendicular to the average wave velocity. The degree of activation by the field (e.g., combustion rate) is related to the current density distribution within the sample, and is therefore related to the temperature-dependent spatial distribution of the effective electrical conductivity of reactants and products. Furthermore, the field can influence other important SHS-related phenomena including capillary flow, mass-transport in porous media, and Marangoni flows. These phenomena are influenced by gravity in conventional SHS processes (i.e., without electric fields). As a result the influence of the field on SHS under reduced gravity is expected to be different than under normal gravity. It is also known that heat loss rates from samples, which can depend significantly on gravity, can influence final products in SHS. This research program is focused on studying field-assisted SHS under reduced gravity conditions. The broad objective of this research program is to understand the role of an electric field in SHS reactions under conditions where gravity-related effects are suppressed. The research will allow increased understanding of fundamental aspects of field-assisted SHS processes as well as synthesis of materials that cannot be formed in normal gravity.

  4. The Influences of Electric Fields on Soot Formation and Flame Structure of Diffusion Flames

    LinXie; TakeyukiKishi; 等

    1993-01-01

    The influences of DC and AC electric fields,at frequencies up to 1.48 MHz and the maximum strength of about 6 kV/cm,on soot formation and flame structure were investigated using a counterflow type acetylene diffusion flame.The distributioons of flame luminosity,soot volume fraction,Flame temperature and OH concentration in flame were measured by non-invasive detection methods.Under the influence of electric fields,the changes in distribution of the soot volume fraction were confirmed.Electric fields of high frequency and high intensity reduced the soot volume fraction.whereas other electric fields increased it.The maximum values of flame temperature and OH concentration decreased.In the relationship between the maximum value of the soot volume fraction and the maximum temperature,the maximum soot volum fraction showed toth increase and decrease with maximum temperatures depending on the frequencies and intensities of the electric fields,and both of them occurred at temperatures lower than 1990 K.The production of the incipient particles seemed to be the dominant process controlling the soot volume fraction due to the electric fields.The luminosity of a sooting diffusion flame was found to depend on the volume fraction and temperature of the soot particles in the flame,As for the behavior of the flame in the electric fields.the ionic wind effect was not found to be dominant in the present work,and the result of the precious simulation based on the ionic wind theory was not consistent with the present experimental results.

  5. Surface electric fields for North America during historical geomagnetic storms

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  6. Hysteretic ac loss in a coated superconductor subjected to oscillating magnetic fields: ferromagnetic effect and frequency dependence

    Numerical simulations of the hysteretic ac loss in a coated superconductor with a more realistic version of the architecture were performed via the finite-element technique in the presence of an oscillating magnetic field. The coated superconductor was electromagnetically modeled by resorting to the quasistatic approximation of a vector potential approach in conjunction with nonlinear descriptions of the superconducting layer and the ferromagnetic substrate therein by a power-law model and the Langevin equation, respectively. A diverse effect of the ferromagnetic substrate on the hysteretic ac loss, depending on the strength of the applied magnetic field, was displayed, and its underlying cause was identified. The dependence of the hysteretic ac loss on the applied frequency is found to be related to a critical amplitude of the applied magnetic field, and the eddy-current loss dissipated in the metal coatings becomes prominent as the frequency increases only at high applied magnetic fields. (paper)

  7. Electric field control of a fluid transfer between freely suspended and sessile droplets

    Choi, Suhwan; Saveliev, Alexei

    2015-11-01

    This works explore direct fluid transfer between microdroplets using liquid bridges stabilized by ac electric field. Experiments are performed with freely and sessile microdroplets of pure glycerol and water with dye. The droplets are placed along electric field directions in a cell with parallel plate electrodes filled with silicone oil. The electrical conductivity of droplets is changed from 1 to 200 μS/cm by adding dye solutions. Liquid bridges interconnecting two microdroplets can be created using an alternating electric field from 0.3 to 0.7 kV/mm with a frequency of 10.3 kHz. For such bridging fluid can be transferred through the liquid bridge from one droplet to another due to the pressure difference. The process is recorded using a CCD camera. The fluid flowrates in the range from ~ 100 to 10 nL/s are recorded with different electric fields and liquid conductivity. We propose that the manipulation of the liquid bridge will be the method in which small fluid volumes are dispensed.

  8. Recent Research Results in the Field of Electric Drives and Mechatronics

    Rastislav Tabacek

    2003-01-01

    Full Text Available The paper presents an overview of research results achieved in the field of Electrical Drives and Mechatronics for the period of three years. The achieved outputs are formed into three individual parts. In the field of Electric Drives the most significant outputs have been achieved in the development of a new control algorithms for a.c. drives under general name 'Forced Dynamics Control' , in improvement of shaft sensorless control methods and in implementation of developed algorithms via digital signal processors. In the field of Electric Traction the most important results have been gained in optimization of power of traction vehicles andat development of diagnostic systems for evaluation of technical conditions of traction devices. In the field of Electric Machines the most important outputs have been achieved in the research of modern electronically commutated electrical machines, their performances in steady and transient states, new design method for their configuration and new methods for automatic parameters identification. In the end the list of the most important publications for all three parts is enclosed.

  9. Spectroscopic measurements of electric field distributions in dielectric barrier discharges in hydrogen

    The results of spectroscopic studies of plasmas generated in dielectric barrier discharges between flat ceramic electrodes supplied by AC voltage in pure hydrogen atmosphere under low-pressure conditions are presented. Stark splitting of the Hα Balmer line was used to measure the electric field strengths in the discharge volume. The optical instrumentation and the detection system allow to perform spatial and time resolved measurements separately for the π and σ Stark components. The measured spatial light intensity distributions are averaged data obtained by integrating signals from many half-periods of the AC voltage supply. This fact has been taken into account when comparing our averaged data with results of theoretical models which are yielding time dependent results

  10. Remote Powering and Steering of Self-Propelling Microdevices by Modulated Electric Field

    Sharma, Rachita; Velev, Orlin

    2011-03-01

    We have demonstrated a new class of self-propelling particles based on semiconductor diodes powered by an external uniform alternating electric field. The millimeter-sized diodes floating in water rectify the applied voltage. The resulting particle-localized electroosmotic flux propels them in the direction of the cathode or the anode depending on their surface charge. These particles suggest solutions to problems facing self-propelling microdevices, and have potential for a range of additional functions. The next step in this direction is the steering of these devices. We will present a novel technique that allows on-demand steering of these self-propelling diodes. We control remotely their direction of motion by modifying the duty cycle of the applied AC field. The diodes change their direction of motion when a DC component (wave asymmetry) is introduced into the AC signal. The DC component leads to redistribution of the counterions near the diode surface. The electric field resulting from this counterion redistribution exerts a torque on the dipole across the diode, causing its rotation. Thus, the reversal of the direction of the electroosmotic flux caused by field asymmetry leads to reversal of the direction of diode motion. This new principle of steering of self-propelling diodes can find applications in MEMs and micro-robotics.

  11. Inner Magnetospheric Electric Fields Derived from IMAGE EUV

    Gallagher, D. L.; Adrian, M. L.

    2007-01-01

    The local and global patterns of plasmaspheric plasma transport reflect the influence of electric fields imposed by all sources in the inner magnetosphere. Image sequences of thermal plasma G:istribution obtained from the IMAGE Mission Extreme Ultraviolet Imager can be used to derive plasma motions and, using a magnetic field model, the corresponding electric fields. These motions and fields directly reflect the dynamic coupling of injected plasmasheet plasma and the ionosphere, in addition to solar wind and atmospheric drivers. What is being learned about the morphology of inner magnetospheric electric fields during storm and quite conditions from this new empirical tool will be presented and discussed.

  12. Electric fields inside and outside an anisotropic dielectric sphere

    Li Ying-Le; Wang Ming-Jun

    2009-01-01

    Analytical expressions of electric fields inside and outside an anisotropic dielectric sphere are presented by transforming an anisotropic medium into an isotropic one based on the multi-scale transformation of electromagnetic theory.The theoretical expressions are consistent with those in the literature. The inside electric field, the outside electric field and the angle between their directions are derived in detail. Numerical simulations show that the direction of the outside field influences the magnitude of the inside field, while the dielectric constant tensor greatly affects its direction.

  13. Gastric applications of electrical field stimulation.

    Hogan, Aisling M

    2012-02-01

    Advances in clinical applications of electricity have been vast since the launch of Hayman\\'s first cardiac pacemaker more than 70 years ago. Gastric electrical stimulation devices have been recently licensed for treatment of gastroparesis and preliminary studies examining their potential for use in refractory obesity yield promising results.

  14. Electric thruster in the space field

    The interest of electric thruster over other techniques of propulsion by reaction is exposed. After a brief mention of the different planetary explorations missions using primary electric propulsion, the use of auxiliary propulsion for the station keeping of geosynchronous satellites is discussed. The principal technologies for the development of ion thrusters (ionization by bombardment and cesium surface ionization) are described and compared

  15. Dipole Relaxation in an Electric Field.

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  16. Kadanoff-Baym approach to time-dependent quantum transport in AC and DC fields

    We have developed a method based on the embedded Kadanoff-Baym equations to study the time evolution of open and inhomogeneous systems. The equation of motion for the Green's function on the Keldysh contour is solved using different conserving many-body approximations for the self-energy. Our formulation incorporates basic conservation laws, such as particle conservation, and includes both initial correlations and initial embedding effects, without restrictions on the time-dependence of the external driving field. We present results for the time-dependent density, current and dipole moment for a correlated tight binding chain connected to one-dimensional non-interacting leads exposed to DC and AC biases of various forms. We find that the self-consistent 2B and GW approximations are in extremely good agreement with each other at all times, for the long-range interactions that we consider. In the DC case we show that the oscillations in the transients can be understood from interchain and lead-chain transitions in the system and find that the dominant frequency corresponds to the HOMO-LUMO transition of the central wire. For AC biases with odd inversion symmetry odd harmonics to high harmonic order in the driving frequency are observed in the dipole moment, whereas for asymmetric applied bias also even harmonics have considerable intensity. In both cases we find that the HOMO-LUMO transition strongly mixes with the harmonics leading to harmonic peaks with enhanced intensity at the HOMO-LUMO transition energy.

  17. The ac quantum Hall resistance as an electrical impedance standard and its role in the SI

    Since 1990, the quantum Hall resistance measured with direct current (dc) has been established to represent and maintain the dc resistance unit and thereby has replaced the former derivation from calculated inductance and capacitance standards. Because of this success, it has been suggested to measure this quantum effect with alternating current (ac) and in this way to derive the units of resistance, capacitance and inductance consistently from the same quantum effect. In this paper, we recall the relations between these units, their role in the determination of the von Klitzing constant and the relations between the fundamental constants involved in the conventional and the quantum approach. Then, we review the first ac measurements of the quantum Hall resistance and show how the difficulties uncovered have been solved by relatively simple means. As a result, the measurement of the ac quantum Hall resistance has become as precise and reliable as its dc counterpart and much more accurate than any conventional impedance artefact. (paper)

  18. On the ionospheric coupling of auroral electric fields

    G. T. Marklund

    2009-01-01

    The quasi-static coupling of high-altitude potential structures and electric fields to the ionosphere is discussed with particular focus on the downward field-aligned current (FAC) region. Results are presented from a preliminary analysis of a selection of electric field events observed by Cluster above the acceleration region. The degree of coupling is here estimated as the ratio between the magnetic field-aligned potential drop, ΔΦII, as inferred fro...

  19. Static and low frequency electric and magnetic fields

    The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people. Static and low frequency electric and magnetic fields may elicit biological reactions. Whether exposure to such fields may affect human health at field strengths present in everyday or occupational life is still unsettled. There is unsufficient knowledge to establish any dose concept relevant to health risk. 196 refs., 6 tabs

  20. Method for electric field and potential calculations in Hall plates

    Raman, Johan; Rombouts, Pieter; Weyten, Ludo

    2013-01-01

    Electrostatic field problems occurring in Hall plates are difficult to solve, mainly because of a non-standard boundary condition defining an oblique angle of the electric field w.r.t. an isolating boundary. A new approach for solving Hall-related field problems is presented. Compared to prior approaches, the technique leads more easily to closed-form expressions for the electric field, and allows obtaining voltage-related Hall characteristics in numerically well conditioned forms.

  1. Strategy of atmospheric electric field and electromagnetic wave measurements by Mars lander

    Takahashi, Yukihiro; Shimizu, Hisayoshi; Ishisaka, Keigo

    Measurement of atmospheric electric field and electromagnetic waves on the ground in Mars is very new and unique approach dedicated not only to the electrical current research but also to the meteorology. Dust devil and storm could be the generator of the currents via dust particle collision process in the very near surface region. If we compare the electric filed near the ground with the dust devil activity, we could clarify the mechanism of dust devil generation. Also the electromagnetic wave measurement makes it possible to know the location and the quantitative strength of dust devil wind only with few observation sites. This measurement also contributes to the studies both on the crust and the upper atmosphere physics. We propose an instrumentation set for the DC and AC electromagnetic observation installed at MArs lander.

  2. Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles

    Gourash, F.

    1984-01-01

    The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.

  3. Study on AC-DC Electrical Conductivities in Warm Dense Matter Generated by Pulsed-power Discharge with Isochoric Vessel

    Sasaki, Toru; Ohuchi, Takumi; Takahashi, Takuya; Kawaguchi, Yoshinari; Saito, Hirotaka; Miki, Yasutoshi; Takahashi, Kazumasa; Kikuchi, Takashi; Aso, Tsukasa; Harada, Nob.

    2016-03-01

    To observe AC and DC electrical conductivity in warm dense matter (WDM), we have demonstrated to apply the spectroscopic ellipsometry for a pulsed-power discharge with isochoric vessel. At 10 μs from the beginning of discharge, the generated parameters by using pulsed-power discharge with isochoric vessel are 0.1 ρ s (ρ s: solid density) of density and 4000 K of temperature, respectively. The DC electrical conductivity for above parameters is estimated to be 104 S/m. In order to measure the AC electrical conductivity, we have developed a four-detector spectroscopic ellipsometer with a multichannel spectrometer. The multichannel spectrometer, in which consists of a 16-channel photodiode array, a two-stages voltage adder, and a flat diffraction grating, has 10 MHz of the frequency response with covered visible spectrum. For applying the four-detector spectroscopic ellipsometer, we observe the each observation signal evolves the polarized behavior compared to the ratio as I 1/I 2.

  4. Rocket borne instrument to measure electric fields inside electrified clouds

    Ruhnke, L. H. (Inventor)

    1973-01-01

    An apparatus for measuring the electric field in the atmosphere which includes a pair of sensors carried on a rocket for sensing the voltages in the atmosphere being measured is described. One of the sensors is an elongated probe with a fine point which causes a corona current to be produced as it passes through the electric field. An electric circuit is coupled between the probe and the other sensor and includes a high ohm resistor which linearizes the relationship between the corona current and the electric field being measured. A relaxation oscillator and transmitter are provided for generating and transmitting an electric signal having a frequency corresponding to the magnitude of the electric field.

  5. Orientation of the agarose gel matrix in pulsed electric fields.

    Stellwagen, J; Stellwagen, N C

    1989-01-01

    The technique of transient electric birefringence was used to investigate the effect of pulsed electric fields on the orientation of the agarose gel matrix. Orientation of the gel was observed at all electric field strengths. Very slow, time-dependent effects were observed when pulses of 10-100 V/cm were applied to 1% gels for 0.5-2 seconds, indicating that domains of the matrix were being oriented by the electric field. The sign of the birefringence reversed when the direction of the applied...

  6. External electric field effect on electron transport in carbon nanotubes

    2012-01-01

    Electronic transport properties of carbon nanotubes are studied theoretically in the presence of external electric field E(t) by using the Boltzmann's transport with constant relaxation time. An analytical expression for the current densities of the nanotubes are obtained. It is observed that the current density-electric field characteristics of the CNs exhibit total self-induced transparency and absolute negative conductivity

  7. On electric field measurements in surface dielectric barrier discharge

    Starikovskaia, S M; Allegraud, K; Guaitella, O; Rousseau, A.

    2010-01-01

    Abstract Analysis of available data on electric field measurements in surface dielectric barrier discharges (DBDs) was carried out. Experimental measurements of emission spectra in triggered and non?triggered sinusoidal surface DBD were performed. The obtained results were used for the calculation of electric field value. The comparison of data obtained and the results published by other authors is presented.

  8. On electric field measurements in surface dielectric barrier discharge

    Starikovskaia, S M; Allegraud, K; Guaitella, O; Rousseau, A, E-mail: svetlana.starikovskaya@lpp.polytechnique.f [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France)

    2010-03-31

    Analysis of available data on electric field measurements in surface dielectric barrier discharges (DBDs) was carried out. Experimental measurements of emission spectra in triggered and non-triggered sinusoidal surface DBD were performed. The results obtained were used for the calculation of electric field value. The comparison of data obtained and the results published by other authors is presented.

  9. High School Students' Representations and Understandings of Electric Fields

    Cao, Ying; Brizuela, Bárbara M.

    2016-01-01

    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields post-instruction as indicated by students'…

  10. Tokamak burn extension by radial electric field control

    This study considers a TFTR-sized plasma operating on a long cycle. The temperature profile is fixed in time, and the plasma is not refuelled. In order to isolate the electric field effects, this last condition is extended to prohibit the electric field at the plasma edge from returning more fuel to the plasma than gradient-driven forces expel

  11. Assessment of magnetic fields exposure from AC power lines in an Italian residential area

    Human exposure to extremely low-frequency (ELF, 30-300 Hz) magnetic fields have recently been suspected of increasing the risk of cancer and leukaemia. The main difficulty in interpreting the available epidemiological data is the assessment of long term exposure to magnetic fields in the ELF range. This assessment of long-term cumulative exposure can be influenced by many factors among which the diurnal and seasonal variations in the electric power use by the line and field spatial variation. To take into account of these factors, different ways of assessing exposure, based on spot measurements or fixed site monitorings, have been used. Because of the importance given by some studies to the frequency dependence of biological effects in the ELF range, the knowledge of magnetic field harmonic contents is of interest to fully characterize the magnetic field exposure. The measurement of the harmonic content is suggested also by the ANSI-IEEE standard to control the possible negative influence of high level harmonic content in the response accuracy of the magnetic field meter. In this work we made a complete characterization of the exposure in a particular italian residential area by using different instrumental chains. The influence of some parameters (spatial and harmonic components of the field, domestic use of the electric power, temporal variability of the field) on the accuracy of the exposure assessment was evaluated

  12. Strong electric fields induced on a sharp stellar boundary

    Mishustin, Igor N.; Ebel, Claudio; Greiner, Walter

    2010-01-01

    Abstract Due to a first order phase transition, a compact star may have a discontinuous distribution of baryon as well as electric charge densities, as e.g. at the surface of a strange quark star. The induced separation of positive and negative charges may lead to generation of supercritical electric fields in the vicinity of such a discontinuity. We study this effect within a relativistic Thomas-Fermi approximation and demonstrate that the strength of the electric field depends strongly o...

  13. Defect agglomeration in ferroelectric ceramics under cyclic electric field

    2008-01-01

    The agglomeration of point defects in ferroelectric ceramics could be driven by repeated domain switching under cyclic electric field. The evolution equation of pore concentration under cyclic electric field is derived, with the help of a relation between the pore concentration and the extent of pore agglomeration. The results of the simulation agree quantitatively with the experimental data. An integrated framework about the mechanisms of electrically induced fatigue is proposed, which links the mechanisms at different scales.

  14. Comments on electric field experiments of positronium formation

    Validity of using static electric field in studying Ps formation mechanism is tested experimentally. At the present experimental condition, Ps intensity in low-density polyethylene was decreased seemingly in a similar way as a function of the strength of static and alternating electric fields. However, a time-dependent screening effect, possibly caused by accumulated charge, was apparent. By using an alternating field, it was possible to eliminate the screening effect. It is highly recommended to use alternating fields in the forthcoming electric field experiments. In another experiment, while applying alternating electric field, PAL was measured only when the polarity was positive or negative with respect to the positron implantation trajectory. The results showed that positive and negative fields have the same effect, indicating that the structure of terminal positron spur is symmetric, unlike the asymmetric structure at the end of muon track

  15. Electric field measurements in the auroral E region

    Dipole electric field, positive ion and electron densities and temperatures, vehicle potential, and plasma sheath measurements have been made in the auroral E region by means of rockets flown from Fort Churchill, Canada. These results are described and compared over the altitude region 100 to 165 km. On a rocket flight launched on 10 December 1969 during very quiet conditions, adjacent to a stable, low intensity auroral arc, the plasma density and temperatures are found to be high and the electric fields large and steady. Electric field components of the order of -17 mv m-1 to +6 mv m-1 were measured along the Earth's magnetic field. The plasma results indicate that these fields may be contributing to enhanced electron temperatures. On a flight of 9 March 1970 during a large magnetic storm with widespread auroral activity, lower plasma densities and temperatures and much smaller and more erratic electric fields were observed with no significant component parallel to the magnetic field. (auth)

  16. Satellite measurements of high latitude convection electric fields.

    Cauffman, D. P.; Gurnett, D. A.

    1972-01-01

    This paper reviews the first results of satellite experiments to measure magnetospheric convection electric fields using the double-probe technique. The earliest successful measurements were made with the low-altitude (680-2530 km) polar orbiting Injun-5 spacecraft. The Injun-5 results are compared with the initial findings of the electric field experiment on the polar orbiting OGO-6 satellite. Electric field measurements from the OGO-6 satellite have substantiated many of the initial Injun-5 observations with improved accuracy and sensitivity. The OGO-6 detector revealed the persistent occurrence of anti-sunward convection across the polar cap region at velocities not generally detectable with the Injun-5 experiment. The OGO-6 observations also provided information indicating that the location of the electric field reversal shifts equatorward during periods of increased magnetic activity. The implications of the electric field measurements for magnetospheric and auroral structure are summarized, and a list of specific recommendations for improving future experiments is presented.

  17. Magnetic phase diagram of graphene nanorings in an electric field

    Magnetic properties of graphene nanorings are investigated in the presence of an electric field. Within the formalism of Hubbard model, the graphene nanorings of various geometric configurations are found to exhibit rich phase diagram. For a nanoring system which has degenerate states at the Fermi level, the system is shown to undergo an abrupt phase transition from the antiferromagnetic to a nonmagnetic state in an electric field applied cross its zigzag edges. However, the nanoring is found to always stay in the antiferromagnetic state when the electric field is applied cross its armchair edges. For the other nanoring system with a finite single-particle gap, the magnetic moments of its antiferromagnetic ground state is seen to decrease gradually to zero with the electric field applied cross the zigzag edges. When the electric field is applied cross the armchair edges, the nanoring is shown to undergo several magnetic phase transitions before settling itself in a nonmagnetic ordering. (paper)

  18. Local-gated single-walled carbon nanotube field effect transistors assembled by AC dielectrophoresis

    We present a simple and scalable technique for the fabrication of solution processed and local-gated carbon nanotube field effect transistors (CNT-FETs). The approach is based on the directed assembly of individual single-walled carbon nanotubes from dichloroethane via AC dielectrophoresis (DEP) onto pre-patterned source and drain electrodes with a local aluminum gate in the middle. Local-gated CNT-FET devices display superior performance compared to a global back gate with on-off ratios >104 and maximum subthreshold swings of 170 mV/dec. The local bottom-gated DEP-assembled CNT-FETs will facilitate large-scale fabrication of complementary metal-oxide-semiconductor (CMOS) compatible nanoelectronic devices

  19. The influence of incompatibility and dielectric contrast on the electric field-induced orientation of lamellar block copolymers

    We investigate the influence of incompatibility and dielectric contrast on the reorientation kinetics of concentrated solutions of lamellar block copolymers in the presence of an external DC electric field. We study solutions of AC diblock copolymer and ABC triblock terpolymers. The inclusion of a short, polar middle block B is used to tailor both the degree of incompatibility and the dielectric contrast between the two majority phases. In situ synchrotron radiation small-angle X-ray scattering is used to monitor the reorientation process. For the AC diblock copolymer sample only weak electric field induced reorientation could be achieved, following a very slow kinetics, whereas for the ABC triblock terpolymer, reorientation is observed above a threshold value of 0.3 kV/mm. The orientation kinetics is well described by a single exponential with characteristic time constants varying between a few seconds and several minutes depending on the polymer concentration and the electric field strength. We identify a narrow concentration window, in which the interplay between chain mobility and gain in free energy in the electric field allows the preparation of highly anisotropic bulk polymer samples by exposure to an electric field. The results are compared to free energy calculations revealing a distinct difference in the driving force for reorientation as a consequence of an increase in dielectric contrast and chain mobility upon introduction of the B middle block.

  20. Module Twelve: Series AC Resistive-Reactive Circuits; Basic Electricity and Electronics Individualized Learning System.

    Bureau of Naval Personnel, Washington, DC.

    The module covers series circuits which contain both resistive and reactive components and methods of solving these circuits for current, voltage, impedance, and phase angle. The module is divided into six lessons: voltage and impedance in AC (alternating current) series circuits, vector computations, rectangular and polar notation, variational…

  1. Effects of geomagnetic activity on the mesospheric electric fields

    A. M. Zadorozhny

    Full Text Available The results of three series of rocket measurements of mesospheric electric fields carried out under different geomagnetic conditions at polar and high middle latitudes are analysed. The measurements show a clear dependence of the vertical electric fields on geomagnetic activity at polar and high middle latitudes. The vertical electric fields in the lower mesosphere increase with the increase of geomagnetic indexes Kp and ∑Kp. The simultaneous increase of the vertical electric field strength and ion conductivity was observed in the mesosphere during geomagnetic disturbances. This striking phenomenon was displayed most clearly during the solar proton events of October, 1989 accompanied by very strong geomagnetic storm (Kp=8+. A possible mechanism of generation of the vertical electric fields in the mesosphere caused by gravitational sedimentation of charged aerosol particles is discussed. Simultaneous existence in the mesosphere of both the negative and positive multiply charged aerosol particles of different sizes is assumed for explanation of the observed V/m vertical electric fields and their behaviour under geomagnetically disturbed conditions.

    Keywords. Atmospheric composition and structure (aerosols and particles · Ionosphere (electric fields and currents · Meteorology and atmospheric dynamics (atmospheric electricity

  2. Enhancement factors for local electric fields in inhomogeneous media

    The microstructure of dielectric films provides a significant influence on the electric field distribution in these materials. In this paper, we focus on the relationship between the electric field distribution and organization of film constituents. Using our self-consistent determination of the local electric field in inhomogeneous media, we have shown that enhanced fields can result from columnar microstructures such as typically generated by CVD-type fabrication processes, and low dielectric components in optical coatings. In addition to the microstructural enhancement, a surface specific enhancement due to presence of low dielectric components is observed

  3. Electrical Effect in Silver-Point Realization Due to Cell Structure and Bias Voltage Based on Resistance Measurement Using AC and DC Bridges

    Widiatmo, J. V.; Harada, K.; Yamazawa, K.; Tamba, J.; Arai, M.

    2015-08-01

    Electrical effects related to insulating leakage represent one of the major factors contributing to uncertainties in measurements using high-temperature standard platinum resistance thermometers (HTSPRTs), especially during the realization of the silver freezing point (). This work is focused on the evaluation of the differences in resistance measurements observed when using AC resistance bridges and DC resistance bridges, hereafter, termed the AC-DC differences, as the result of various electrical effects. The magnitude of the AC-DC difference in several silver-point cells is demonstrated with several HTSPRTs. The effect of the cell structure on the AC-DC difference is evaluated by exchanging some components, part by part, within a silver-point cell. Then, the effect of the bias voltage applied to the heat pipe within the silver-point furnace is evaluated. Through the analysis of the experimental results and comparison with the reports in the literature, the importance of evaluating the AC-DC difference as a means to characterize the underlying electrical effects is discussed, considering that applying a negative bias condition to the furnace with respect to the high-temperature SPRT can minimize the AC-DC difference. Concluding recommendations are proposed on the components used in silver-point cells and the application of a bias voltage to the measurement circuit to minimize the effects of the electrical leakage.

  4. Effects of an electric field on white sharks: in situ testing of an electric deterrent.

    Charlie Huveneers

    Full Text Available Elasmobranchs can detect minute electromagnetic fields, <1 nV cm(-1, using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7™ electric deterrent on (1 the behaviour of 18 white sharks (Carcharodon carcharias near a static bait, and (2 the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks.

  5. Electron electric dipole moment experiment using electric-field quantized slow cesium atoms

    Amini, Jason M.; Munger Jr., Charles T.; Gould, Harvey

    2007-01-01

    A proof-of-principle electron electric dipole moment (e-EDM) experiment using slow cesium atoms, nulled magnetic fields, and electric field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/m lifts the degeneracy between states of unequal lbar mF rbar and, along with the low (approximately 3 m/s) velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small r...

  6. Signal amelioration of electrophoretically deposited whole-cell biosensors using external electric fields

    Highlights: → We present an electrochemical whole-cell biochip that can apply electric fields. → We examine the integration of cells on a biochip using electrophoretic deposition. → The effect of electric fields on the whole-cell biosensor has been demonstrated. → Relatively short DC electric pulse improves the performance of whole-cell biosensors. → Prolonged AC electric fields deteriorated the whole-cell biosensor performance. - Abstract: This paper presents an integrated whole-cell biochip system where functioning cells are deposited on the solid micro-machined surfaces while specially designed indium tin oxide electrodes that can be used to apply controllable electric fields during various stages; for example during cell deposition. The electrodes can be used also for sensing currents associated with the sensing mechanisms of electrochemical whole-cell biosensors. In this work a new approach integrating live bacterial cells on a biochip using electrophoretic deposition is presented. The biomaterial deposition technique was characterized under various driving potentials and chamber configurations. An analytical model of the electrophoretic deposition kinetics was developed and presented here. The deposited biomass included genetically engineered bacterial cells that may respond to toxic material exposure by expressing proteins that react with specific analytes generating electrochemically active byproducts. In this study the effect of external electric fields on the whole-cell biochips has been successfully developed and tested. The research hypothesis was that by applying electric fields on bacterial whole-cells, their permeability to the penetration of external analytes can be increased. This effect was tested and the results are shown here. The effect of prolonged and short external electric fields on the bioelectrochemical signal generated by sessile bacterial whole-cells in response to the presence of toxins was studied. It was demonstrated that

  7. Kerr electrooptic tomography for determination of nonuniform electric field distributions in dielectrics

    Ustundag, Afsin

    The electrical breakdown strength of insulating materials is the limiting factor for greater efficiencies in AC, DC and pulse power apparatus and systems. To improve high voltage designs and prevent failures it is necessary to understand the physics of charge injection and transport and electrical breakdown phenomena. Kerr electro-optic measurements utilize the applied electric field induced anisotropy in refractive index. The anisotropy affects light propagation through the dielectric so that light intensity measurements provide information on electric field distributions which cannot be calculated from knowledge of the geometry alone due to unknown space charge distributions. Most past Kerr electro-optic measurements have been limited to cases where the electric field direction and magnitude are constants along the light path allowing simple relationships between measured light intensity and electric field. This thesis analyzes the more general case when the applied electric field magnitude and direction vary along the light path. An approximate slow spatial variation form of Maxwell equations is obtained as the governing equations of light propagation in Kerr media and extensively analyzed. It is shown that from each light intensity measurement it is possible to obtain three characteristic parameters when the medium is highly birefringent and the electrode geometry has no symmetry, and two characteristic parameters when the medium is weakly birefringent and/or the geometry is axisymmetric. The characteristic parameters are related to the applied electric field for which new generalized Kerr electro- optic measurement techniques were developed. Three classes of algorithms for the inverse problem of reconstructing electric field distributions from Kerr electro-optic data are investigated. We developed a finite element method based reconstruction algorithm which is applicable to arbitrary three-dimensional geometries when the medium is weakly birefringent. For

  8. Electric Field-Mediated Processing of Polymers. Appendix 1

    Wnek, G. E.; Bowlin, G. L.; Haas, T. W.

    2000-01-01

    Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. We suggest that a broad range of properties can be achieved using a relatively small number of polymers, with electric fields providing the ability to tailor properties via the control of shape, morphology, and orientation. Specific attention is given to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options.

  9. Solving the electrical control of magnetic coercive field paradox

    Vopson, Melvin; Lepadatu, S.

    2014-01-01

    The ability to tune magnetic properties of solids via electric voltages instead of external magnetic fields is a physics curiosity of great scientific and technological importance. Today, there is strong published experimental evidence of electrical control of magnetic coercive fields in composite multiferroic solids. Unfortunately, the literature indicates highly contradictory results. In some studies, an applied voltage increases the magnetic coercive field and in other studies the applied ...

  10. On the correlation analysis of electric field inside jet engine

    KRISHNA A.; Khattab, T.; Abdelaziz, A.F.; Guizani, M.

    2014-01-01

    A Simple channel modeling method based on correlation analysis of the electric field inside jet engine is presented. The analysis of the statistical propagation characteristics of electromagnetic field inside harsh jet engine environment is presented by using `Ansys® HFSS'. In this paper, we propose a method to locate the best position for receiving probes inside jet engine with minimum correlation between the receiver points which have strong average electric field. Moreover, a MIMO system c...

  11. Numerical Simulation of Modified Radial Electric Field by LHCD

    Wei Wei; Ding Bojiang; Kuang Guangli

    2005-01-01

    Based on the electron's radial force equilibrium, the profiles of radial electric field in OH and LHCD phase are calculated by using a simulation code. The dependences of radial electron field on electron density and its profile and different current ratio, Irf/Ip, are given. The connections between the improvement of plasma confinement and the modified radial electric field by LHCD are discussed by comparing the calculated results with the experimental results.

  12. Electric characterization of (Sr, Sr-Ba, Ba) M-type ferrites by AC measurements[Alternating Current

    Huanosta-Tera, A.; Lira-Hueso, R. de; Perez-Orta, O.; Palomares-Sanchez, S.A.; Ponce-Castaneda, S.; Mirabal-Garcia, M.

    2000-02-01

    Considering the electrical conductivity in ceramics, necessary reference should be given to dynamic processes occurring as a function of frequency and temperature. Although the most immediate interest in ferrites lies in their magnetic properties, technological applications require a wider knowledge of general physical properties as well. This is especially applicable when the materials are studied as a function of composition or when adding different modifiers. In this report, the authors present results of the ac and dc electric characteristics of a family of magneto-plumbite-type hexaferrites, where Ba gradually substitutes Sr in the Ba{sub x}Sr{sub 1{minus}x}Fe{sub 12}O{sub 19} compound (0 {le} x {le} 1). The results were determined over a wide range of frequencies and temperatures.

  13. Aharonov-Casher phase shift and the change in velocity of a moving magnet traversing an electric field

    Motivated by the theoretical work of Boyer [J. Phys. A: Math. Gen. 39 (2006) 3455] plus the quite recent interferometric experiment of Shinohara, Aoki and Morinaga [Phys. Rev. A66 (2002) 042106] in which the scalar Aharonov-Bohm effect was studied, we re-open the extension to neutral particles carrying a magnetic moment and passing through a region of intense electric field, treated theoretically by Aharonov and Casher (AC) and independently by Anandan. An alternative interpretation of results on (a) neutrons and (b) TlF molecules to that afforded by AC is shown to involve only (i) the de Broglie wavelength of matter waves and (ii) the prediction from Maxwell's equations for the change in velocity of a neutral moving magnet as it enters or leaves an electric field. The exquisite sensitivity of experiment (b) allows a fractional change in velocity of order 10-15 to be quantitatively determined. (author)

  14. dc electric field meter with fiber-optic readout

    Johnston, Alan R.; Kirkham, Harold; Eng, Bjorn T.

    1986-01-01

    The design of a dc electric field meter capable of measuring the magnitude and direction of the electric field at an arbitrary location above the ground plane is described. The meter is based on measuring induced charge on a split cylindrical electrode pair which is rotated around its axis of symmetry. Data readout is by fiber-optic cable using pulse frequency encoding. The sensing head is electrically isolated. Initial results are reported from a series of tests at General Electric's High Voltage Transmission Research Facility, Pittsfield, MA. The electric field was measured in a large test cage and under a dc test line. Measurement of field magnitude and direction around a human subject standing under the conductor was demonstrated.

  15. Determinants of the electric field during transcranial direct current stimulation

    Opitz, Alexander; Paulus, Walter; Will, Susanne;

    2015-01-01

    Transcranial direct current stimulation (tDCS) causes a complex spatial distribution of the electric current flow in the head which hampers the accurate localization of the stimulated brain areas. In this study we show how various anatomical features systematically shape the electric field...... over the motor cortex in small steps to examine the resulting changes of the electric field distribution in the underlying cortex. We examined the effect of skull thickness and composition on the passing currents showing that thinner skull regions lead to higher electric field strengths. This effect...... fluid and the skull, the gyral depth and the distance to the anode and cathode. These factors account for up to 50% of the spatial variation of the electric field strength. Further, we demonstrate that individual anatomical factors can lead to stimulation "hotspots" which are partly resistant...

  16. Mechanosensory hairs in bumblebees (Bombus terrestris) detect weak electric fields.

    Sutton, Gregory P; Clarke, Dominic; Morley, Erica L; Robert, Daniel

    2016-06-28

    Bumblebees (Bombus terrestris) use information from surrounding electric fields to make foraging decisions. Electroreception in air, a nonconductive medium, is a recently discovered sensory capacity of insects, yet the sensory mechanisms remain elusive. Here, we investigate two putative electric field sensors: antennae and mechanosensory hairs. Examining their mechanical and neural response, we show that electric fields cause deflections in both antennae and hairs. Hairs respond with a greater median velocity, displacement, and angular displacement than antennae. Extracellular recordings from the antennae do not show any electrophysiological correlates to these mechanical deflections. In contrast, hair deflections in response to an electric field elicited neural activity. Mechanical deflections of both hairs and antennae increase with the electric charge carried by the bumblebee. From this evidence, we conclude that sensory hairs are a site of electroreception in the bumblebee. PMID:27247399

  17. Combined effects of intense laser field, electric and magnetic fields on the nonlinear optical properties of the step-like quantum well

    In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change for transition between two lower-lying electronic levels in the step-like GaAs/Ga1−xAlxAs quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. - Highlights: • Augmentation of laser-field results in red shift in total AC spectra. • Magnetic field induces a blue-shift in the resonant peak. • Resonant peak position shifts to red with effect of electric field. • Resonant peak of total AC shifts to the higher photon energies with increasing well width

  18. Combined effects of intense laser field, electric and magnetic fields on the nonlinear optical properties of the step-like quantum well

    Kasapoglu, E., E-mail: ekasap@cumhuriyet.edu.tr [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Restrepo, R.L. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Escuela de Ingeniería de Antioquia-EIA, Medellín (Colombia); Ungan, F.; Yesilgul, U.; Sari, H. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Sökmen, I. [Department of Physics, Dokuz Eylül University, 35160 Buca, İzmir (Turkey)

    2015-03-15

    In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change for transition between two lower-lying electronic levels in the step-like GaAs/Ga{sub 1−x}Al{sub x}As quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. - Highlights: • Augmentation of laser-field results in red shift in total AC spectra. • Magnetic field induces a blue-shift in the resonant peak. • Resonant peak position shifts to red with effect of electric field. • Resonant peak of total AC shifts to the higher photon energies with increasing well width.

  19. Electric field mapping inside metallized film capacitors

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Failure mode and effect analysis (FMEA) is an important step in the reliability assessment process of electric components. It provides knowledge of the physics of failure of a component that has been subjected to a given stress profile. This knowledge enables improvement of the component robustness...... of the metallization stripes had lost contact to the end-spray. Thus, it is shown that the surface electric potential distributions on micro-sectioned film capacitors can be obtained through KPFM analysis. We have, from KPFM measurements, shown that the degraded capacitors under investigation had suffered from...

  20. Electric field gradients in Hg compounds

    Arcisauskaité, Vaida; Knecht, Stefan; Sauer, Stephan P. A.;

    2012-01-01

    We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved by compar......We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved...

  1. Enhanced electrical properties of ferroelectric thin films with electric field induced domain control

    (0 0 1) oriented Pb(Zr0.5Ti0.5)O3 (PZT) thin films with high piezoelectric constant were deposited by the electric field-assisted annealing (EFA-A) of alkoxide-derived precursor thin films. So far, selective orientation control of (0 0 1) domain and (1 0 0) domain is very difficult, especially for the chemical solution deposition (CSD). We tried an electric field induced domain control to improve the electrical properties with CSD. An electric field of 10 kV/cm has been applied during an annealing. The high (0 0 1) domain ratio of 75.6% was obtained from the deconvolution of (0 0 2) and (2 0 0) X-ray diffraction peaks. The PZT thin films showed very high piezoelectric constant of 352 pm/V. This shows electric field induced domain control is very effective to enhance the electrical properties of CSD-derived PZT thin films.

  2. AC loss of HTS magnet for AMR refrigerator using magnetic field formulation and edge element in cylindrical coordinates

    Kim, Seo Ho; Park, Minwon [Changwon National University, Changwon (Korea, Republic of); Jeong, Sang Kwon [KAIST, Daejeon (Korea, Republic of)

    2013-05-15

    AMR (Active Magnetic Regenerative) refrigerators require the large variation of the magnetic field and a HTS magnet can be used. The amount of AC loss is very important considering the overall efficiency of the AMR refrigerator. However, it is very hard to estimate the precise loss of the HTS magnet because the magnetic field distribution around the conductor itself depends on the coil configuration and the neighboring HTS wires interact each other through the distorted magnetic field by the screening current Therefore, the AC loss of HTS magnet should be calculated using the whole configuration of the HTS magnet with superconducting characteristic. This paper describes the AC loss of the HTS magnet by an appropriate FEM approach, which uses the non-linear characteristic of HTS conductor. The analysis model is based on the 2-D FEM model, called as 'magnetic field formulation and edge-element model', for whole coil configuration in cylindrical coordinates. The effects of transport current and stacked conductors on the AC loss are investigated considering the field-dependent critical current. The PDE model of 'Comsol multiphysics' is used for the FEM analysis with properly implemented equations for axisymmetric model.

  3. The relationship between anatomically correct electric and magnetic field dosimetry and published electric and magnetic field exposure limits

    Electric and magnetic field exposure limits published by International Commission for Non-Ionizing Radiation Protection and Inst. of Electrical and Electronics Engineers are aimed at protection against adverse electro-stimulation, which may occur by direct coupling to excitable tissue and, in the case of electric fields, through indirect means associated with surface charge effects (e.g. hair vibration, skin sensations), spark discharge and contact current. For direct coupling, the basic restriction (BR) specifies the not-to-be-exceeded induced electric field. The key results of anatomically based electric and magnetic field dosimetry studies and the relevant characteristics of excitable tissue were first identified. This permitted us to assess the electric and magnetic field exposure levels that induce dose in tissue equal to the basic restrictions, and the relationships of those exposure levels to the limits now in effect. We identify scenarios in which direct coupling of electric fields to peripheral nerve could be a determining factor for electric field limits. (authors)

  4. Characteristics of AC capillary discharge produced in electrically conductive water solution

    De Baerdemaeker, F.; Šimek, Milan; Schmidt, Jiří; Leys, C.

    2007-01-01

    Roč. 16, č. 2 (2007), s. 341-354. ISSN 0963-0252 R&D Projects: GA AV ČR IAA1043102 Institutional research plan: CEZ:AV0Z20430508 Keywords : water breakdown * capillary * AC discharge * conductive liquid * optical emission * decay time * vapour bubble * breakdown mechanism Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.120, year: 2007

  5. The effect of electrical conductivity on the growth of the electric field in a thunderstorm

    Levin, Z.; W. D. Scott

    2011-01-01

    The effect of the electrical conductivity on the electrical development of the cloud is investigated. By the use of a numerical model which couples the growth of the electric field and the precipitation development it is demonstrated that as long as the conductivity varies between values which are smaller than the fair weather conductivity and values of up to 100 times the fair weather conductivity, the polarization charging mechanism is powerful enough to generate fields large enough to crea...

  6. Electrical conductivity of single-wall carbon nanotube films in strong electric field

    Seliuta, D; Subačius, L; Kašalynas, I; Shuba, M.; Paddubskaya, A.

    2013-01-01

    (Received 6 March 2013; accepted 26 April 2013; published online 14 May 2013) Carrier transport features in single-wall carbon nanotube (SWCNT) films under strong electric fields (up to 105 V/cm) are presented. Application of electrical pulses of nanosecond duration allowed to minimize Joule heating and resolve intrinsic nonlinearities with the electric field. Investigations within a wide range of temperatures—4.2–300 K—indicated that carrier localization as well as tunneling t...

  7. Electron electric-dipole-moment experiment using electric-field quantized slow cesium atoms

    A proof-of-principle electron electric-dipole-moment (e-EDM) experiment using slow cesium atoms, nulled magnetic fields, and electric-field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/m lifts the degeneracy between states of unequal |mF| and, along with the low (≅3 m/s) velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small residual magnetic field have made it possible to induce transitions between states and to perform state preparation, analysis, and detection in regions free of applied static magnetic and electric fields. This experiment demonstrates techniques that may be used to improve the e-EDM limit by two orders of magnitude, but it is not in itself a sensitive e-EDM search, mostly due to limitations of the laser system

  8. Electron electric dipole moment experiment using electric-field quantized slow cesium atoms

    Amini, Jason M; Gould, Harvey

    2007-01-01

    A proof-of-principle electron electric dipole moment (e-EDM) experiment using slow cesium atoms, nulled magnetic fields, and electric field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/m lifts the degeneracy between states of unequal mF and, along with the low (approximately 3 m/s) velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small residual magnetic field have made it possible to induce transitions between states and to perform state preparation, analysis, and detection in regions free of applied static magnetic and electric fields. This experiment demonstrates techniques that may be used to improve the e-EDM limit by two orders of magnitude, but it is not in itself a sensitive e-EDM search, mostly due to limitations of the laser system.

  9. Effect of nanosilica on optical, electric modulus and AC conductivity of polyvinyl alcohol/polyaniline films

    Nanosilica (NS) was synthesized by a sol–gel method and mixed with 0.98 polyvinyl alcohol (PVA)/0.02 polyaniline (PANI) in different amounts to produce nanocomposite films. High-resolution transmission electron microscopy (HR-TEM) revealed the average particle size of the NS to be ca. 15 nm. Scanning electron microscopy (SEM) showed that the NS was well-dispersed on the surface of the PVA/PNAI films. The Fourier transform infrared (FTIR) spectra of the samples showed a significant change in the intensity of the characteristic peak of the functional groups in the composite films with the amount of NS added. The absorbance and refractive index (n) of the composites were studied in the UV–vis range, and the optical energy band gap, Eg, and different optical parameters were calculated. The dielectric loss modulus, M″ and ac conductivity, σac, of the samples were studied within 300–425 K and 0.1 kHz–5 MHz, respectively. Two relaxation peaks were observed in the frequency dependence of the dielectric loss modulus, M″. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work are discussed and compared with those of previous studies of similar composites

  10. Galvanotactic behavior of Tetrahymena pyriformis under electric fields

    Tetrahymena pyriformis, a eukaryotic ciliate, swims toward a cathode in straight or cross-shaped microchannels under an applied electric field, a behavioral response called cathodal galvanotaxis. In straight channel experiments, a one-dimensional electric field was applied, and the galvanotactic swimming behavior of Tetrahymena pyriformis was observed and described in detail while the polarity of this field is switched. In most individual cases, the cell would immediately switch its direction toward the cathode; however, exceptional cases have been observed where cells exhibit a turning delay or do not turn after a polarity switch. In cross-channel experiments, feedback control using vision-based tracking was used to steer a cell in the microchannel intersection using a two-dimensional electric field generated by four electrodes placed at four ends of the cross channel. The motivation for this work is to study the swimming behavior of Tetrahymena pyriformis as a microrobot under the control of electric fields. (paper)

  11. Optical Remote Sensing of Electric Fields Above Thunderstorms

    Burns, B. M.; Carlson, B. E.; Lauben, D.; Cohen, M.; Smith, D.; Inan, U. S.

    2010-12-01

    Measurement of thunderstorm electric fields typically require balloon-borne measurements in the region of interest. Such measurements are cumbersome and provide limited information at a single point. Remote sensing of electric fields by Kerr-effect induced optical polarization changes of background skylight circumvents many of these difficulties and can in principle provide a high-speed movie of electric field behavior. Above-thundercloud 100 kV/m quasi-static electric fields are predicted to produce polarization changes at above the part in one million level that should be detectable at a ground instrument featuring 1 cm2sr geometric factor and 1 kHz bandwidth (though more sensitivity is nonetheless desired). Currently available optical and electronic components may meet these requirements. We review the principles of this measurement and discuss the current status of a field-ready prototype instrument currently in construction.

  12. Electron propagation in crossed magnetic and electric fields

    Kramer, T; Kleber, M; Kramer, Tobias; Bracher, Christian; Kleber, Manfred

    2004-01-01

    Laser-atom interaction can be an efficient mechanism for the production of coherent electrons. We analyze the dynamics of monoenergetic electrons in the presence of uniform, perpendicular magnetic and electric fields. The Green function technique is used to derive analytic results for the field--induced quantum mechanical drift motion of i) single electrons and ii) a dilute Fermi gas of electrons. The method yields the drift current and, at the same time it allows us to quantitatively establish the broadening of the (magnetic) Landau levels due to the electric field: Level number k is split into k+1 sublevels that render the $k$th oscillator eigenstate in energy space. Adjacent Landau levels will overlap if the electric field exceeds a critical strength. Our observations are relevant for quantum Hall configurations whenever electric field effects should be taken into account.

  13. Improved Approximations for Fermion Pair Production in Inhomogeneous Electric Fields

    Kim, S P; Kim, Sang Pyo; Page, Don N.

    2007-01-01

    Reformulating the instantons in a complex plane for tunneling or transmitting states, we calculate the pair-production rate of charged fermions in a spatially localized electric field, illustrated by the Sauter electric field E_0 (sech)^2 (z/L), and for a temporally localized electric field such as E_0 (sech)^2 (t/T). The integration of the quadratic part of WKB instantons over the frequency and transverse momentum leads to the pair-production rate obtained by the worldline instanton method including the prefactor of Phys. Rev. D 72, 105004 (2005) and 73, 065028 (2006). It is further shown that the WKB instanton plus the next-to-leading order contribution in spinor QED equals the WKB instanton in scalar QED, thus justifying why the WKB instanton in scalar QED can work for pair production of fermions. Finally we obtain the pair-production rate in a spatially localized electric field together with a constant magnetic field.

  14. Scattering and pair creation by L-constant electric field

    Gavrilov, S P

    2015-01-01

    Using QFT approach developed by us in Ref. arXiv:1506.01156, we consider particle scattering and vacuum instability in the so-called L-constant electric field, which is a constant electric field confined between two capacitor plates separated by a finite distance L. We obtain and analyze special sets of stationary solutions of the Dirac and Klein-Gordon equations with the L-constant electric field. Then, we represent probabilities of particle scattering and characteristics of the vacuum instability (related to the pair creation) in terms of the introduced solutions. From exact formulas, we derive asymptotic expressions for the differential mean numbers, for the total mean number of created particles, and for the vacuum-to-vacuum transition probability. Using the equivalence principle, we demonstrate that the distributions of created particles by L-constant electric field and gravitational field of a black hole have similar thermal structure.

  15. Electromechanical analysis of tapered piezoelectric bimorph at high electric field

    Chattaraj, Nilanjan; Ganguli, Ranjan

    2015-04-01

    Piezoelectric bimorph laminar actuator of tapered width exhibits better performance for out-of-plane deflection compared to the rectangular surface area, while consuming equal surface area. This paper contains electromechanical analysis and modeling of a tapered width piezoelectric bimorph laminar actuator at high electric field in static state. The analysis is based on the second order constitutive equations of piezoelectric material, assuming small strain and large electric field to capture its behavior at high electric field. Analytical expressions are developed for block force, output strain energy, output energy density, input electrical energy, capacitance and energy efficiency at high electric field. The analytical expressions show that for fixed length, thickness, and surface area of the actuator, how the block force and output strain energy gets improved in a tapered surface actuator compared to a rectangular surface. Constant thickness, constant length and constant surface area of the actuator ensure constant mass, and constant electrical capacitance. We consider high electric field in both series and parallel electrical connection for the analysis. Part of the analytical results is validated with the experimental results, which are reported in earlier literature.

  16. High Dynamic Range Electric Field Sensor for Electromagnetic Pulse Detection

    Lin, Che-Yun; Lee, Beom Suk; Zhang, Xingyu; Chen, Ray T

    2014-01-01

    We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.

  17. Interferometric methods for mapping static electric and magnetic fields

    Pozzi, Giulio; Beleggia, Marco; Kasama, Takeshi;

    2014-01-01

    The mapping of static electric and magnetic fields using electron probes with a resolution and sensitivity that are sufficient to reveal nanoscale features in materials requires the use of phase-sensitive methods such as the shadow technique, coherent Foucault imaging and the Transport of Intensity...... on theoretical models that form the basis of the quantitative interpretation of electron holographic data. We review the application of electron holography to a variety of samples (including electric fields associated with p–n junctions in semiconductors, quantized magnetic flux in superconductors......) the model-independent determination of the locations and magnitudes of field sources (electric charges and magnetic dipoles) directly from electron holographic data....

  18. The source of the electric field in the nightside magnetosphere

    In the open magnetosphere model magnetic field lines from the polar caps connect to the interplanetary magnetic field and conduct an electric field from interplanetary space to the polar ionosphere. By examining the magnetic flux involved it is concluded that only slightly more than half of the magnetic flux in the polar caps belongs to open field lines and that such field lines enter or leave the magnetosphere through narrow elongated windows stretching the tail. These window regions are identified with the tail's boundary region and shift their position with changes in the interplanetary magnetic field, in particular when a change of interplanetary magnetic sector occurs. The circuit providing electric current in the magnetopause and the plasma sheet is extended across those windows; thus energy is drained from the interplanetary electric field and an electric potential drop is produced across the plasma sheet. The polar cap receives its electric field from interplanetary space on the day side from open magnetic field lines and on the night side from closed field lines leading to the plasma sheet. The theory described provides improved understanding of magnetic flux bookkeeping, of the origin of Birkeland currents, and of the boundary layer of the geomagnetic tail. (Author)

  19. Parallel and orthogonal E-field alignment of single-walled carbon nanotubes by ac dielectrophoresis

    We designed planar electrodes, for dielectrophoretic manipulation of single-walled carbon nanotubes (SWNTs), built as metal-oxide-semiconductor nanogap capacitors with common substrate and oxide thicknesses of 17 and 150 nm. Such design generates high electric fields (109 V m-1) and also the fringing field is curved due to the conducting substrate, unlike fields generated by conventionally used planar electrodes. Scanning electron microscopy images showed SWNTs aligned parallel and perpendicular to the electrodes. Raman spectroscopic mapping was used to produce separate images of the metallic (m-SWNT) and semiconducting (s-SWNT) nanotube density distributions. As expected, parallel alignment of the m-SWNTs with the E-field was found; however, also a perpendicular alignment of s-SWNTs was observed. Such orthogonal alignment of s-SWNTs is a rare observation and has not been experimentally reported before in detail with Raman images. Due to the unique electrode design, we were able to obtain substantial separation of m-SWNTs and s-SWNTs. Numerical modeling of the electric field factor of the dielectrophoresis force was done, and it matched perfectly with the experimental results. The orthogonal alignment of s-SWNTs results from comparable values of parallel and perpendicular polarizability to the nanotube axis.

  20. Electric field induced instabilities in free emulsion films

    Tchoukov, P.; Dabros, T. [Natural Resources Canada, Devon, AB (Canada); Mostowfi, F. [Schlumberger DBR Technology Center, Edmonton, AB (Canada); Panchev, N. [Champion Technologies Inc., Houston, TX (United States); Czarnecki, J. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

    2009-07-01

    This presentation reported on a study that investigated the mechanism of electric field-induced breakdown of free emulsion films. Instability patterns were observed on the plane of a water-oil-water film following electric polarization. The length-scales of the instabilities were measured by analyzing images immediately after applying the electric field. Linear stability analysis was used to calculate the theoretical dominant wavelengths. The calculated values were found to be in good agreement with measured values. The films were formed in a thin film apparatus modified so that the oil film separated 2 aqueous phase compartments, each in contact with a platinum electrode. This enabled the measurement of disjoining pressure while applying the electric field to the film. It was concluded that breakdown of thin films induced by electric field has many applications, including electrostatic de-emulsification/desalination of crude oil and emulsion stability measurements. It was concluded that electroporation and dielectric breakdown may be responsible for electric field-induced breakdown. This study also presented evidence of an increase in electric field-induced instabilities in emulsion films resulting in rupture. tabs., figs.

  1. Electric fields are novel determinants of human macrophage functions.

    Hoare, Joseph I; Rajnicek, Ann M; McCaig, Colin D; Barker, Robert N; Wilson, Heather M

    2016-06-01

    Macrophages are key cells in inflammation and repair, and their activity requires close regulation. The characterization of cues coordinating macrophage function has focused on biologic and soluble mediators, with little known about their responses to physical stimuli, such as the electrical fields that are generated naturally in injured tissue and which accelerate wound healing. To address this gap in understanding, we tested how properties of human monocyte-derived macrophages are regulated by applied electrical fields, similar in strengths to those established naturally. With the use of live-cell video microscopy, we show that macrophage migration is directed anodally by electrical fields as low as 5 mV/mm and is electrical field strength dependent, with effects peaking ∼300 mV/mm. Monocytes, as macrophage precursors, migrate in the opposite, cathodal direction. Strikingly, we show for the first time that electrical fields significantly enhance macrophage phagocytic uptake of a variety of targets, including carboxylate beads, apoptotic neutrophils, and the nominal opportunist pathogen Candida albicans, which engage different classes of surface receptors. These electrical field-induced functional changes are accompanied by clustering of phagocytic receptors, enhanced PI3K and ERK activation, mobilization of intracellular calcium, and actin polarization. Electrical fields also modulate cytokine production selectively and can augment some effects of conventional polarizing stimuli on cytokine secretion. Taken together, electrical signals have been identified as major contributors to the coordination and regulation of important human macrophage functions, including those essential for microbial clearance and healing. Our results open up a new area of research into effects of naturally occurring and clinically applied electrical fields in conditions where macrophage activity is critical. PMID:26718542

  2. Electric field mapping inside metallized film capacitors

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Failure mode and effect analysis (FMEA) is an important step in the reliability assessment process of electric components. It provides knowledge of the physics of failure of a component that has been subjected to a given stress profile. This knowledge enables improvement of the component robustness and durability and serves as verification that failure- and degradation mechanisms remain the same at different stress levels during accelerated testing. In this work we have used Kelvin probe forc...

  3. Near-optimal order-reduced control for A/C (air-conditioning) system of EVs (electric vehicles)

    This work is aimed to investigate the regulation problem for thermal comfortableness and propose control strategies for cabin environment of EVs (electric vehicles) by constructing a reduced-scale A/C (air-conditioning) system which mainly consists of two modules: ECB (environmental control box) and AHU (air-handling unit). Temperature and humidity in the ECB can be regulated by AHU via cooling, heating, mixing air streams and adjusting speed of fans. To synthesize the near-optimal controllers, the mathematical model for the system thermodynamics is developed by employing the equivalent lumped heat capacity approach, energy/mass conservation principle and the heat transfer theories. In addition, from the clustering pattern of system eigenvalues, the thermodynamics of the interested system can evidently be characterized by two-time-scale property. That is, the studied system can be decoupled into two subsystems, slow mode and fast mode, by singular perturbation technique. As to the optimal control strategies for EVs, by taking thermal comfortableness, humidity and energy consumption all into account, a series of optimal controllers is synthesized on the base of the order-reduced thermodynamic model. The feedback control loop for the experimental test rig is examined and realized by the aid of the control system development kit dSPACE DS1104 and the commercial software MATLAB/Simulink. To sum up, the intensive computer simulations and experimental results verify that the performance of the near-optimal order-reduced control law is almost as superior as that of standard LQR (Linear-Quadratic Regulator). - Highlights: • A reduced-scale test rig for A/C (air-conditioning) system to imitate the temperature/humidity of cabin in EV (electric vehicle) is constructed. • The non-linear thermodynamic model of A/C system can be decoupled by singular perturbation technique. • The temperature/humidity in cabin is regulated to the desired values by proposed optimal

  4. Ettingshausen effect of superconducting fluctuations at high electric fields

    Full text: We extend the calculations of the non-ohmic fluctuation transport properties of layered superconductors to the Ettingshausen effect with respect to a strong in-plane electric field under the presence of a magnetic field perpendicular to the layers. The Ettingshausen coefficient is inferred beyond the linear-response approximation, by calculating the heat current density generated along the direction perpendicular to both the out-of-plane magnetic field and the in-plane electric field, in the self-consistent Hartree approach of the time-dependent Ginzburg-Landau equation, for an arbitrarily strong electric field. We illustrate the results of the model on typical high-temperature superconductors, like optimally doped YBa2Cu3O6+x and Bi2Sr2CaCu2O8+x, and predict an important suppression of the Ettingshausen effect due to the high electric field, much stronger than the effect of the magnetic field alone. At higher magnetic fields, the fluctuation suppression due to the electric field becomes however relatively smaller. (author)

  5. Electric and magnetic fields in medicine and biology

    Papers Include: The effects of low frequency (50 Hz) magnetic fields on neuro-chemical transmission in vitro; Morphological changes in E Coli subjected to DC electrical fields; An investigation of some claimed biological effects of electromagnetic fields; Electrical phenomena and bone healing - a comparison of contemporary techniques; Clinical evaluations of a portable module emitting pulsed RF energy; The design, construction and performance of a magnetic nerve stimulator; The principle of electric field tomography and its application to selective read-out of information from peripheral nerves; Applied potential tomography - clinical applications; Impendance imaging using a linear electrode array; Mathematics as an aid to experiment: human body currents induced by power frequency electric fields; Effects of electric field near 750KV transmission line and protection against their harmful consequences; Leukemia and electromagnetic fields: a case-control study; Overhead power lines and childhood cancer; Magnetic measurement of nerve action currents - a new intraoperative recording technique; The potential use of electron spin resonance or impedance measurement to image neuronal electrical activity in the human brain

  6. The bee, the flower and the electric field

    Robert Daniel

    2016-01-01

    Full Text Available Insects use several different senses to forage on flowers, and detect floral cues such as color, shape, pattern, humidity and chemical volatiles. This presentation will present our discovery of a previously unappreciated sensory capacity in bumblebees (Bombus terrestris: the detection of floral electric fields. We show that these floral fields act as informational cues, and that they can be affected by the visit of naturally electrically charged bees. Like visual cues, floral electric fields exhibit variations in pattern and structure, which can be discriminated by bumblebees. We also show that such electric field information contributes to the complex array of floral cues that together improve a pollinator’s memory of floral rewards. Floral electric fields arise from complex interactions with the surrounding atmosphere, an interaction between plants and their environment that not well understood. Because floral electric fields can change within seconds, this new sensory modality - electrostatic field detection- may facilitate rapid and dynamic communication between flowers and their pollinators.

  7. Semiclassical pair production rate for rotating electric fields

    Strobel, Eckhard

    2014-01-01

    We semiclassically investigate Schwinger pair production for pulsed rotating electric fields depending on time. To do so we solve the Dirac equation for two-component fields in a WKB-like approximation. The result shows that for two-component fields the spin distribution of produced pairs is generally not $1:1$. As a result the pair creation rates of spinor and scalar quantum electro dynamics (QED) are different even for one pair of turning points. For rotating electric fields the pair creation rate is dominated by particles with a specific spin depending on the sense of rotation. We present an analytical solution for the momentum spectrum of the constant rotating field. We find interference effects not only in the momentum spectrum but also in the total particle number of rotating electric fields.

  8. Monte Carlo simulations of air showers in atmospheric electric fields

    Buitink, S; Falcke, H; Heck, D; Kuijpers, J

    2009-01-01

    The development of cosmic ray air showers can be influenced by atmospheric electric fields. Under fair weather conditions these fields are small, but the strong fields inside thunderstorms can have a significant effect on the electromagnetic component of a shower. Understanding this effect is particularly important for radio detection of air showers, since the radio emission is produced by the shower electrons and positrons. We perform Monte Carlo simulations to calculate the effects of different electric field configurations on the shower development. We find that the electric field becomes important for values of the order of 1 kV/cm. Not only can the energy distribution of electrons and positrons change significantly for such field strengths, it is also possible that runaway electron breakdown occurs at high altitudes, which is an important effect in lightning initiation.

  9. Effective critical electric field for runaway electron generation

    Stahl, Adam; Decker, Joan; Embréus, Ola; Fülöp, Tünde

    2014-01-01

    In this letter we investigate factors that influence the effective critical electric field for runaway electron generation in plasmas. We present numerical solutions of the kinetic equation, and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway formation often is higher than previously calculated due to both (1) extremely strong dependence of primary generation on temperature, and (2) synchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field.

  10. Long period preservation of marine products using electrostatic field

    Okumura, Takamasa; Yaegashi, Taro; Yamada, Kazuki; Ito, Takanori; Takahashi, Katsuyuki; Aisawa, Sumio; Takaki, Koichi; Yamazaki, Shigeyoshi; Syuto, Bunei

    2016-07-01

    The effect of an AC electric field on the freshness of marine products was experimentally investigated. An AC voltage of 10 kV with 50 Hz in frequency was generated with a transformer and applied to a plane electrode set in an incubator. The biological material was the gonad of purple sea urchin. The AC electric field with 50 Hz in frequency was applied to the gonad at ‑1 °C for 7 days. Freshness was evaluated by measuring protein release and lactate dehydrogenase (LDH) activity. The results showed that the protein release and LDH activity in the gonad were suppressed by applying the AC electric field, compared with that without the AC electric field. Moreover, the gonad was treated with the AC electric field at ‑5 °C for 3 days and then preserved at 0 °C for 1 day without the field. This electrical field treatment of the gonad prolonged the freshness date for more than 10 days under 4 °C preservation condition. In addition, the permeability of the cell membrane was suppressed by applying the AC electric field. Concerning the relationship between permeability and AC electric field, the conformational change of bovine serum albumin (BSA) induced by the AC electric field was evaluated on the basis of UV absorption spectra. The results revealed that the secondary and/or higher-order structure gradually changes with preservation period. The conformational change of the BSA molecule was induced by applying the AC electric field.

  11. Laser spectroscopic measurement of electric field structure induced in plasma-edges in magnetic field

    A new laser-induced fluorescence (LIF) technique was developed to directly measure the electric field distribution with high spatial resolution in plasma edges under magnetic field. As a model-type experiment, sheath electric field distribution was measured in front of a biased metal plate inserted into an ECR helium plasma flow under magnetic field. Good agreement was obtained between the potential difference over the sheath determined from the measured distribution and the applied bias voltage. Applicability of our LIF technique to the case of strong magnetic field was discussed. Detectable range of the electric field is estimated. (author)

  12. Communication: Control of chemical reactions using electric field gradients.

    Deshmukh, Shivaraj D; Tsori, Yoav

    2016-05-21

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts. PMID:27208928

  13. Communication: Control of chemical reactions using electric field gradients

    Deshmukh, Shivaraj D.; Tsori, Yoav

    2016-05-01

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  14. Induction effects on ionospheric electric and magnetic fields

    H. Vanhamäki

    2005-07-01

    Full Text Available Rapid changes in the ionospheric current system give rise to induction currents in the conducting ground that can significantly contribute to magnetic and especially electric fields at the Earth's surface. Previous studies have concentrated on the surface fields, as they are important in, for example, interpreting magnetometer measurements or in the studies of the Earth's conductivity structure. In this paper we investigate the effects of induction fields at the ionospheric altitudes for several realistic ionospheric current models (Westward Travelling Surge, Ω-band, Giant Pulsation. Our main conclusions are: 1 The secondary electric field caused by the Earth's induction is relatively small at the ionospheric altitude, at most 0.4 mV/m or a few percent of the total electric field; 2 The primary induced field due to ionospheric self-induction is locally important, ~ a few mV/m, in some "hot spots", where the ionospheric conductivity is high and the total electric field is low. However, our approximate calculation only gives an upper estimate for the primary induced electric field; 3 The secondary magnetic field caused by the Earth's induction may significantly affect the magnetic measurements of low orbiting satellites. The secondary contribution from the Earth's currents is largest in the vertical component of the magnetic field, where it may be around 50% of the field caused by ionospheric currents.

    Keywords. Geomagnetism and paleomagnetism (geomagnetic induction – Ionosphere (electric fields and currents

  15. Electric field in media with power-law spatial dispersion

    Tarasov, Vasily E.

    2016-04-01

    In this paper, we consider electric fields in media with power-law spatial dispersion (PLSD). Spatial dispersion means that the absolute permittivity of the media depends on the wave vector. Power-law type of this dispersion is described by derivatives and integrals of non-integer orders. We consider electric fields of point charge and dipole in media with PLSD, infinite charged wire, uniformly charged disk, capacitance of spherical capacitor and multipole expansion for PLSD-media.

  16. Spiral Wave Generation in a Vortex Electric Field

    YUAN Xiao-Ping; CHEN Jiang-Xing; ZHAO Ye-Hua; LOU Qin; WANG Lu-Lu; SIIEN Qian

    2011-01-01

    The effect of a vortical electric field on nonlinear patterns in excitable media is studied. When an appropriate vortex electric field is applied, the system exhibits pattern transition from chemical turbulence to spiral waves, which possess the same chtality as the vortex electric field. The underlying mechanism of this is discussed. We also show the meandering behavior of a spiral under the taming of a vortex electric field. The results obtained here may contribute to control strategies of patterns on surface reaction.%The effect of a vortical electric field on nonlinear patterns in excitable media is studied.When an appropriate vortex electric field is applied,the system exhibits pattern transition from chemical turbulence to spiral waves,which possess the same chirality as the vortex electric field.The underlying mechanism of this is discussed.We also show the meandering behavior of a spiral under the taming of a vortex electric field.The results obtained here may contribute to control strategies of patterns on surface reaction.Spiral waves are one of the most common and widely studied patterns in nature.They appear in hydrodynamic systems,chemical reactions and a large variety of biological,chemical and physical systems.[1-5] Much attention has been paid to their rich nonlinear dynamics,as well as potential applications in various biological or physiological systems,since the emergence and instability of spirals usually lead to abnormal states,for example in cardiac arrythmia[6,7] and epilepsy[8].Much research has been carried out in studying pattern formations in catalytic CO oxidation on Pt(110),[9-11] because they provide practical utilization in industry.A rich variety of spatiotemporal patterns,including travelling pulses,standing waves,target patterns,spiral waves and chemical turbulence have been observed in this system.[12-16

  17. Ionizing gas breakdown waves in strong electric fields.

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  18. Critical fluctuation conductivity in layered superconductors in strong electric field

    Puica, I.; Lang, W.

    2003-01-01

    The paraconductivity, originating from critical superconducting order-parameter fluctuations in the vicinity of the critical temperature in a layered superconductor is calculated in the frame of the self-consistent Hartree approximation, for an arbitrarily strong electric field and zero magnetic field. The paraconductivity diverges less steep towards the critical temperature in the Hartree approximation than in the Gaussian one and it shows a distinctly enhanced variation with the electric fi...

  19. Electric field-dependent charge transport in organic semiconductors

    Li, Ling; Van Winckel, Steven; Genoe, Jan; Heremans, Paul

    2009-01-01

    An analytical description is elaborated for the variable range hopping conduction mechanism in the presence of temperature and electric fields for quasi-three-dimensional organic semiconductor systems. In the proposed description, it is assumed that the localized states are randomly distributed in energy and space coordinates. The expression for the hopping conductivity is obtained for the Gaussian density of states. The model is applied to the analysis of both temperature and electric field-...

  20. Effects Of Electric Field On Hydrocarbon-Fueled Flames

    Yuan, Z.-G.; Hegde, U.

    2003-01-01

    It has been observed that flames are susceptible to electric fields that are much weaker than the breakdown field strength of the flame gases. When an external electric field is imposed on a flame, the ions generated in the flame reaction zone drift in the direction of the electric forces exerted on them. The moving ions collide with the neutral species and change the velocity distribution in the affected region. This is often referred to as ionic wind effect. In addition, the removal of ions from the flame reaction zone can alter the chemical reaction pathway of the flame. On the other hand, the presence of space charges carried by moving ions affects the electric field distribution. As a result, the flame often changes its shape, location and color once an external electric field is applied. The interplay between the flame movement and the change of electric field makes it difficult to determine the flame location for a given configuration of electrodes and fuel source. In normal gravity, the buoyancy-induced flow often complicates the problem and hinders detailed study of the interaction between the flame and the electric field. In this work, the microgravity environment established at the 2.2 Second Drop Tower at the NASA Glenn Research Center is utilized to effectively remove the buoyant acceleration. The interaction between the flame and the electric field is studied in a one-dimensional domain. A specially designed electrode makes flame current measurements possible; thus, the mobility of ions, ion density, and ionic wind effect can be evaluated.

  1. Calculations of the Electric Fields in Liquid Solutions

    Fried, Stephen D; Wang, Lee-Ping; Boxer, Steven G.; Ren, Pengyu; Pande, Vijay S.

    2013-01-01

    The electric field created by a condensed phase environment is a powerful and convenient descriptor for intermolecular interactions. Not only does it provide a unifying language to compare many different types of interactions, but it also possesses clear connections to experimental observables, such as vibrational Stark effects. We calculate here the electric fields experienced by a vibrational chromophore (the carbonyl group of acetophenone) in an array of solvents of diverse polarities usin...

  2. An Optimal Electric Dipole Antenna Model and Its Field Propagation

    Xu, Yidong; Guo, Lili; Xue, Wei; Vladimir, Korochentsev; Qi, Junwei

    2016-01-01

    An optimal electric dipole antennas model is presented and analyzed, based on the hemispherical grounding equivalent model and the superposition principle. The paper also presents a full-wave electromagnetic simulation for the electromagnetic field propagation in layered conducting medium, which is excited by the horizontal electric dipole antennas. Optimum frequency for field transmission in different depth is carried out and verified by the experimental results in comparison with previously...

  3. Evolution of Spiral Waves under Modulated Electric Fields

    MA Jun; YING He-Ping; PAN Guo-Wei; PU Zhong-Sheng

    2005-01-01

    @@ Spirals generated from the excitable media within the Barkley model is investigated under the gradient electric fields by a numerical simulation. The spiral drift and spiral break up are observed when the amplitude of the electric fields is modulated by a constant signal or a chaotic signal. It is also verified that, even in the presence of the white noise, the whole system can reach homogeneous states after the spiral breakup, by using an adaptive strategy.

  4. Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

    Bandler, Simon

    2011-01-01

    At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

  5. Detailed modelling of screening currents, their magnetic field and AC loss in coated conductor magnets containing up to 40000 turns

    Pardo, Enric

    2016-01-01

    Screening currents caused by varying magnetic fields degrade the homogeneity and stability of the magnetic fields created by $RE$BCO coated conductor coils. They are responsible for the AC loss, which is also important for other power applications containing windings. Since real magnets contain coils exceeding 10000 turns, accurate modeling tools for this number of turns are necessary for magnet design. This article presents a fast numerical method to model coils with no loss of accuracy. We ...

  6. The chromatographic separation of particles using optical electric fields

    Javier Alvarez, Nicolas; Jeppesen, Claus; Yvind, Kresten;

    2013-01-01

    We introduce a new field-flow fractionation (FFF) technique, whereby molecules are separated based on their differential interaction (dielectrophoresis (DEP)) with optical electric fields, i.e. electric fields with frequencies in the visible and near-infrared range. The results show that a parallel...... array of axially non-uniform optical fields yielding an attractive potential (positive-DEP-FFF) is advantageous for the separation of polymers, biomolecules, and nanoparticles over very short distances. Furthermore, positive-DEP-FFF yields superior selectivity and resolution compared to conventional...

  7. Effect of superheat and electric field on saturated film boiling

    Pandey, Vinod; Biswas, Gautam; Dalal, Amaresh

    2016-05-01

    The objective of this investigation is to study the influence of superheat temperature and applied uniform electric field across the liquid-vapor interface during film boiling using a coupled level set and volume of fluid algorithm. The hydrodynamics of bubble growth, detachment, and its morphological variation with electrohydrodynamic forces are studied considering the medium to be incompressible, viscous, and perfectly dielectric at near critical pressure. The transition in interfacial instability behavior occurs with increase in superheat, the bubble release being periodic both in space and time. Discrete bubble growth occurs at a smaller superheat whereas vapor columns form at the higher superheat values. Destabilization of interfacial motion due to applied electric field results in decrease in bubble separation distance and increase in bubble release rate culminating in enhanced heat transfer rate. A comparison of maximum bubble height owing to application of different intensities of electric field is performed at a smaller superheat. The change in dynamics of bubble growth due to increasing superheat at a high intensity of electric field is studied. The effect of increasing intensity of electric field on the heat transfer rate at different superheats is determined. The boiling characteristic is found to be influenced significantly only above a minimum critical intensity of the electric field.

  8. Spiking patterns of a hippocampus model in electric fields

    We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy. (interdisciplinary physics and related areas of science and technology)

  9. Spiking patterns of a hippocampus model in electric fields

    Men Cong; Wang Jiang; Qin Ying-Mei; Wei Xi-Le; Che Yan-Qiu; Deng Bin

    2011-01-01

    We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective.Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study.The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity.It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field.Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude.These findings are qualitatively in accordance with the results of relevant experimental and numerical studies.It is implied that the external or endogenous electric field can modulate the neural code in the brain.Furthermore,it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.

  10. Migration of amoeba cells in an electric field

    Guido, Isabella; Bodenschatz, Eberhard

    2015-03-01

    Exogenous and endogenous electric fields play a role in cell physiology as a guiding mechanism for the orientation and migration of cells. Electrotaxis of living cells has been observed for several cell types, e.g. neurons, fibroblasts, leukocytes, neural crest cells, cancer cells. Dictyostelium discoideum (Dd), an intensively investigated chemotactic model organism, also exhibits a strong electrotactic behavior moving toward the cathode under the influence of electric fields. Here we report experiments on the effects of DC electric fields on the directional migration of Dd cells. We apply the electric field to cells seeded into microfluidic devices equipped with agar bridges to avoid any harmful effects of the electric field on the cells (ions formation, pH changes, etc.) and a constant flow to prevent the build-up of chemical gradient that elicits chemotaxis. Our results show that the cells linearly increase their speed over time when a constant electric field is applied for a prolonged duration (2 hours). This novel phenomenon cannot be attributed to mechanotaxis as the drag force of the electroosmotic flow is too small to produce shear forces that can reorient cells. It is independent of the cellular developmental stage and to our knowledge, it was not observed in chemotaxis. This work is supported by MaxSynBio project of the Max Planck Society.

  11. Ponderomotive Force in the Presence of Electric Fields

    Khazanov, G. V.; Krivorutsky, E. N.

    2013-01-01

    This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E cross B drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.

  12. Ponderomotive force in the presence of electric fields

    This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E(vector sign)×B(vector sign) drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.

  13. Enhance soil bioremediation with electric fields

    Electrokinetic remediation is an in situ remediation technique that uses low-level direct-current electric potential differences (on the order of volts per centimeter) or an electric current (on the order of milliamps per square centimeter of cross-sectional area between electrodes) applied across a soil mass by electrodes placed in an open- or closed-flow arrangement. In electrokinetic methods, the groundwater in the boreholes or an externally supplied fluid (processing fluid) is used as the conductive medium. Electrokinetic remediation technology for metal extraction is expected to decrease the cost of remediating contaminated soils to the lower end of the $100--$1,000/m3 range. This would be a significant savings in the $350 billion hazardous waste site cleanup and remediation market. The environmental restoration cost for the mixed (radioactive)-waste market is separately estimated to be $65 billion. The potential of the electrokinetic remediation technique in remediating soils contaminated with radioactive mixed waste using depolarization agents and complexing agents is noteworthy. The authors have removed uranyl ions from spiked kaolinite using the technique

  14. Impedance characteristics for solid Ag/AgCl electrode used as recording electric field generated by vessels in seawater

    ZHANG Yan; WANG Yuan-sheng; SONG Yusu

    2009-01-01

    Ag/AgCl electrode has been prepared using pressed powder techniques. In order to verify the feasibility of this type of electrode used as detecting electric field generated by vessels in seawater, its characteristics of DC resistance, low frequency AC impedance, and receiving impedance in artificial seawater have been studied by polarization measurements, low frequency electrochemical impedance spectra, the open and short circuit cell conditions. The results show that the electrode can keep a low resistance when it responses the weak electrostatic field in seawater. The AC impedance of the electrode decreases as the frequency of the signal increasing. The receiving impedance decreases when the frequency of external field increases too. The valid detection bandwidth is determined by the properties of the impedance and the reactions occurring on the surface of the electrode.

  15. Physical and electrical models for interpreting AC and DC transport measurements in polymer solar cells

    McIntyre, Max; Tzolov, Marian; Cossel, Raquel; Peeler, Seth

    We have fabricated and studied bulk heterojunction solar cells using a mixture of the low bandgap material PCPDTBT and PCBM-C60. Our transport studies show that the devices in dark have good rectification and they respond to AC voltage as a simple RC circuit. The illumination causes an additional contribution to the impedance, which varies with the level of illumination. One proposed model is that photo-generated charges can become trapped in potential wells. These charges then follow a Debye relaxation process, which contributes to a varying dielectric constant. Another proposed model is based on a RC circuit model with two capacitors which can describe the varying capacitance behavior. The physical mechanism for this model is that photo-generated charges become accumulated at the interface between PCPDTBT and PCBM-C60 and form an additional layer of charge. We will show that our circuit models and their analogous physical models can predict the AC and DC responses of polymer solar cells.

  16. Electrical properties of AC3B4O12-type perovskite ceramics with different cation vacancies

    Highlights: • AC3B4O12 perovskite with different concentration cation vacancies were prepared. • Cell parameter decreases with the increase of concentration of cation vacancies. • PTCO and CTO remain high dielectric permittivity but depress loss greatly. • Dielectric loss associates with cation vacancies and motion of oxygen vacancies. - Abstract: AC3B4O12-type perovskite CaCu3Ti4O12 (CCTO), □0.34Pr0.67Cu3Ti4O12 (PCTO), □1Cu3Ta2Ti2O12 (CTTO), □2Cu2Ta4O12 (CTO) ceramics with different concentration cation vacancies were prepared through traditional solid state reaction method. X-ray diffraction analysis indicated that CCTO and PCTO are perovskite cubic with space group Im-3 (no. 204) while CTTO and CTO are Pm-3 (no. 200). Cell parameter of the samples dramatically increases with the increase of cation vacancies. Dielectric permittivity of them maintains very high value of ∼104 from room temperature to 550 K but the dielectric loss is depressed with the increase of cation vacancies in the same space group. The dielectric properties and conductivity behavior were described by the Debye relaxation and the universal dielectric response, respectively. The effect mechanism of cation vacancy and crystal structure on carrier transposition were discussed

  17. Effects of AC/DC magnetic fields, frequency, and nanoparticle aspect ratio on cellular transfection of gene vectors

    Ford, Kris; Mair, Lamar; Fisher, Mike; Rowshon Alam, Md.; Juliano, Rudolph; Superfine, Richard

    2008-10-01

    In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane.

  18. Electric fields and plasma waves resulting from a barium injection experiment

    A shaped-charge, barium plasma injection experiment was performed in June 1976 from the DOE Kauai test facility. The rocket payload contained seven shaped charges, a sevenfold larger package than the typical payloads employed in previous barium plasma injections conducted in this program. An attitude control system oriented the injection perpendicular to the local geomagnetic field. The injection altitude was 450 km. The second-stage motor section contained a payload to measure dc and ac electric fields using a 5-m-long, tip-to-tip dual spherical probe antenna. The ac electric field frequency response was from 100 Hz to 12 kHz. The dc channel responds up to 160 Hz. Shortly after the detonation, the dc electric field was parallel to the geomagnetic field. A few seconds later the measured electric field was the v x B field induced by the motion of the antenna through the plasma. A variety of plasma waves were detected for approximately 20 s following the injection. The initial impulse in the dc channel was measured to be 115 mV/m. The injection generated barium cyclotron waves at 3.4, 7.2, and 10.6 Hz. The barium gyrofrequency at the altitude of the injection was 3.3 Hz. The initial amplitude at 3.4 Hz was 25 mV/m peak-to-peak. These waves were evident in the data for approximately 6 s. Between 3 and 8 after the explosion, band-limited noise was intermittently present between 1.6 and 3.2 kHz. These emissions were lower-hybrid-resonance emissions in a barium plasma. The instability responsible for these emissions is tentatively identified as the modified two-stream instability. Wide-band noise with a decreasing intensity as a function of frequency in the band from 100 Hz to 5 kHz was present from 4 to 30 s following the explosion. The intensity maximized when the antenna was most nearly parallel to the geomagnetic field. This suggests that the waves were ion acoustic waves. Highly structured emission occurred between 500 Hz for several seconds after the explosion

  19. A high sensitivity calibrated electric field meter based on the electric potential sensor

    An electric field measurement system with a maximum sensitivity of 2.6 µV m−1 and an associated accuracy of 2% is described. It is based on the ultra-high input impedance electric potential sensor and is calibrated using a test structure of well-defined geometry to establish a calculable electric field. Finite element simulations are used to verify the field geometry and include the effect of finite boundary conditions due to the proximity of grounded structures. These are found to have a considerable effect on the uniformity of the field. The agreement seen between the measurements and simulations is achieved using a single numerical calibration factor and indicates that the presence of the sensor causes no significant perturbation of the electric field

  20. Physics-Based Modeling of Electric Operation, Heat Transfer, and Scrap Melting in an AC Electric Arc Furnace

    Opitz, Florian; Treffinger, Peter

    2016-04-01

    Electric arc furnaces (EAF) are complex industrial plants whose actual behavior depends upon numerous factors. Due to its energy intensive operation, the EAF process has always been subject to optimization efforts. For these reasons, several models have been proposed in literature to analyze and predict different modes of operation. Most of these models focused on the processes inside the vessel itself. The present paper introduces a dynamic, physics-based model of a complete EAF plant which consists of the four subsystems vessel, electric system, electrode regulation, and off-gas system. Furthermore the solid phase is not treated to be homogenous but a simple spatial discretization is employed. Hence it is possible to simulate the energy input by electric arcs and fossil fuel burners depending on the state of the melting progress. The model is implemented in object-oriented, equation-based language Modelica. The simulation results are compared to literature data.

  1. Electric field and temperature effects in irradiated MOSFETs

    Silveira, M. A. G.; Santos, R. B. B.; Leite, F. G.; Araújo, N. E.; Cirne, K. H.; Melo, M. A. A.; Rallo, A.; Aguiar, Vitor. A. P.; Aguirre, F.; Macchione, E. L. A.; Added, N.; Medina, N. H.

    2016-07-01

    Electronic devices exposed to ionizing radiation exhibit degradation on their electrical characteristics, which may compromise the functionality of the device. Understanding the physical phenomena responsible for radiation damage, which may be specific to a particular technology, it is of extreme importance to develop methods for testing and recovering the devices. The aim of this work is to check the influence of thermal annealing processes and electric field applied during irradiation of Metal Oxide Semiconductor Field Effect Transistors (MOSFET) in total ionizing dose experiments analyzing the changes in the electrical parameters in these devices

  2. Electric Field-Responsive Mesoporous Suspensions: A Review

    Seung Hyuk Kwon

    2015-12-01

    Full Text Available This paper briefly reviews the fabrication and electrorheological (ER characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress.

  3. Low magnetic Johnson noise electric field plates for precision measurement

    Rabey, I M; Hinds, E A; Sauer, B E

    2016-01-01

    We describe a parallel pair of high voltage electric field plates designed and constructed to minimise magnetic Johnson noise. They are formed by laminating glass substrates with commercially available polyimide (Kapton) tape, covered with a thin gold film. Tested in vacuum, the outgassing rate is less than $5\\times10^{-5}$ mbar.l/s. The plates have been operated at electric fields up to 8.3 kV/cm, when the leakage current is at most a few hundred pA. The design is discussed in the context of a molecular spin precession experiment to measure the permanent electric dipole moment of the electron.

  4. Electric field-induced softening of alkali silicate glasses

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown

  5. Electric field-induced softening of alkali silicate glasses

    McLaren, C.; Heffner, W.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Tessarollo, R.; Raj, R. [Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309 (United States)

    2015-11-02

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  6. Rydberg-Stark states in oscillating electric fields

    Zhelyazkova, V

    2015-01-01

    Experimental and theoretical studies of the effects of weak radio-frequency electric fields on Rydberg-Stark states with electric dipole moments as large as 10000 D are reported. High-resolution laser spectroscopic studies of Rydberg states with principal quantum number $n=52$ and $53$ were performed in pulsed supersonic beams of metastable helium with the excited atoms detected by pulsed electric field ionisation. Experiments were carried out in the presence of sinusoidally oscillating electric fields with frequencies of 20~MHz, amplitudes of up to 120~mV/cm, and dc offsets of up to 4.4~V/cm. In weak fields the experimentally recorded spectra are in excellent agreement with the results of calculations carried out using Floquet methods to account for electric dipole couplings in the oscillating fields. This highlights the validity of these techniques for the accurate calculation of the Stark energy level structure in such fields, and the limitations of the calculations in stronger fields where $n-$mixing and ...

  7. Electric field by pick-up ions and electrons

    Yamauchi, Masatoshi; Behar, Etienne; Nilsson, Hans; Holmstrom, Mats

    2016-04-01

    Observations by the Rosetta Plasma Consortium (RPC) showed increasing distortion of the solar wind flow as Rosetta approached the Sun, i.e., as the density of the newly born ions increased. This indicates azimuthal momentum transfer from the solar wind to the newly born ions because they are displaced by the solar wind electric field up to the ion gyroradius this the solar wind velocity, and conservation of the momentum (center of the mass) makes the solar wind to azimuthally shift by "counter action" of these pick-up ion motions. To understand this azimuthal momentum transfer, it is inevitable to model the electric field by the displacement of these pick-up ions and electrons. Although the E×B drift does not make charge separation when the scale size is larger than the ion gyroradius, ions and electrons move in the opposite direction to each other within the short distance up to a gyroradius, and therefore, the charge separation occurs. Thus, the newly-ionized neutrals (ion-electron pairs) create the electric field in the opposite (shielding) direction to the solar wind electric field (like the ionopause of Venus and Mars). However, such a newly induced "shielding" electric field will simultaneously be weakened by the solar wind electrons because the solar wind is also moved by this shielding electric field to reduce it, in the same way as the plasma oscillation (time scale of about 10‑4 s). In other words, the solar wind tries to maintain the solar wind electric field as far as the momentum allows. These two opposite effects must be combined when modelling the azimuthal electric field, and resultant ion/electron motions within a gyroradius, like the case for ROSETTA. Furthermore, the effect of the induced electric field by the pick-up ions and electrons will be different when the newly born ions are created as the result of photo-ionization and of the charge exchange because the electron effect is different between them. In the presentation, we model the

  8. Strong electric fields induced on a sharp stellar boundary

    Mishustin, Igor N; Greiner, Walter

    2010-01-01

    Due to a first order phase transition, a compact star may have a discontinuous distribution of baryon as well as electric charge densities, as e.g. at the surface of a strange quark star. The induced separation of positive and negative charges may lead to generation of supercritical electric fields in the vicinity of such a discontinuity. We study this effect within a relativistic Thomas-Fermi approximation and demonstrate that the strength of the electric field depends strongly on the degree of sharpness of the surface. The influence of strong electric fields on the stability of compact stars is discussed. It is demonstrated that stable configurations appear only when the counter-pressure of degenerate fermions is taken into consideration.

  9. Time development of electric fields and currents in space plasmas

    A. T. Y. Lui

    2006-05-01

    Full Text Available Two different approaches, referred to as Bu and Ej, can be used to examine the time development of electric fields and currents in space plasmas based on the fundamental laws of physics. From the Bu approach, the required equation involves the generalized Ohm's law with some simplifying assumptions. From the Ej approach, the required equation can be derived from the equation of particle motion, coupled self-consistently with Maxwell's equation, and the definition of electric current density. Recently, some strong statements against the Ej approach have been made. In this paper, we evaluate these statements by discussing (1 some limitations of the Bu approach in solving the time development of electric fields and currents, (2 the procedure in calculating self-consistently the time development of the electric current in space plasmas without taking the curl of the magnetic field in some cases, and (3 the dependency of the time development of magnetic field on electric current. It is concluded that the Ej approach can be useful to understand some magnetospheric problems. In particular, statements about the change of electric current are valid theoretical explanations of change in magnetic field during substorms.

  10. Electric fields, weighting fields, signals and charge diffusion in detectors including resistive materials

    Riegler, Werner

    2016-01-01

    In this report we discuss static and time dependent electric fields in detector geometries with an arbitrary number of parallel layers of a given permittivity and weak conductivity. We derive the Green's functions i.e. the field of a point charge, as well as the weighting fields for readout pads and readout strips in these geometries. The effect of 'bulk' resistivity on electric fields and signals is investigated. The spreading of charge on thin resistive layers is also discussed in detail, a...

  11. Vector Control Algorithm for Electric Vehicle AC Induction Motor Based on Improved Variable Gain PID Controller

    Gang Qin

    2015-01-01

    Full Text Available The acceleration performance of EV, which affects a lot of performances of EV such as start-up, overtaking, driving safety, and ride comfort, has become increasingly popular in recent researches. An improved variable gain PID control algorithm to improve the acceleration performance is proposed in this paper. The results of simulation with Matlab/Simulink demonstrate the effectiveness of the proposed algorithm through the control performance of motor velocity, motor torque, and three-phase current of motor. Moreover, it is investigated that the proposed controller is valid by comparison with the other PID controllers. Furthermore, the AC induction motor experiment set is constructed to verify the effect of proposed controller.

  12. Studies on AC Electrical Conductivity of CdCl2 Doped PVA Polymer Electrolyte

    M. B. Nanda Prakash

    2013-01-01

    Full Text Available PVA-based polymer electrolytes were prepared with various concentrations of CdCl2 using solvent casting method. Prepared polymer films were investigated using line profile analysis employing X-ray diffraction (XRD data. XRD results show that the crystallite size decreases and then increases with increase in CdCl2. AC conductivity in these polymer increases films first and then decreases. These observations are in agreement with XRD results. The highest ionic conductivity of 1.68E − 08 Scm−1 was observed in 4% of CdCl2 in PVA polymer blend. Crystallite ellipsoids for different concentrations of CdCl2 are computed here using whole pattern powder fitting (WPPF indicating that crystallite area decreases with increase in the ionic conductivity.

  13. Magnetostriction behaviour of Fe-Co-V alloy strips in the presence of DC and AC magnetic fields

    High magnetostriction Fe-Co-V alloy strips used in scale breakers were prepared by hot rolling process with the ingots which were made using the vacuum arc melting method. The effect of vanadium concentration on the DC magnetostriction behaviour and on the hot workability were investigated in the ternary Fe50-x-Co50-xV2x (0 49Co49V2 alloy strip was compared with the AC magnetostriction in the presence of 60 Hz AC magnetic fields. The influence of stress on the AC magnetic behaviour of Fe49Co49V2 alloy strips which were heat-treated at 750oC after hot rolling was investigated for both tensile and compressive stresses.The amount of saturated magnetostriction (λs) is increased by replacing cobalt and iron with vanadium in Fe50Co50 alloy, but the hot workability of Fe-Co-V alloys restricts vanadium concentration to 2 wt.% for industrial applications. The amount of AC magnetostriction for an Fe49Co49V2 alloy strip was shown to be higher than the DC magnetostriction at the same magnetic field intensity and magnetostriction was found to be in the presence of compressive stress than in conditions of a tensile one. (author)

  14. Asymmetry of Neoclassical Transport by Dipole Electric Field

    王中天; 王龙

    2004-01-01

    Effects of dipole electric fields on neoclassical transport are studied. Large asymmetry in transport is created. The dipole fields, which are in a negative R-direction, reduce the ion drift, increase electron drift, and change the steps of excursion due to collisions. It is found that different levels of dipole field intensities have different types of transport. For the lowest level of the dipole field, the transport returns to the neoclassical one. For the highest level of the dipole field, the transport is turned to be the turbulence transport similar to the pseudo-classical transport. Experimental data may be corresponded to a large level of the dipole field intensity.

  15. On a Correlation between the Ionospheric Electric Field and the Time Derivative of the Magnetic Field

    R. R. Ilma

    2012-01-01

    Full Text Available A correlation of the ionospheric electric field and the time derivative of the magnetic field was noticed over thirty years ago and has yet to be explained. Here we report on another set of examples during the superstorm of November 2004. The electric field in the equatorial ionosphere, measured with the Jicamarca incoherent scatter radar, exhibited a 3 mV/m electric field pulse that was not seen in the interplanetary medium. It was, however, accompanied by a correlation with the time derivative of the magnetic field measured at two points in Peru. Our inclination was to assume that the field was inductive. However, the time scale of the pulse was too short for the magnetic field to penetrate the crust of the Earth. This means that the area threaded by ∂B/∂t was too small to create the observed electric field by induction. We suggest that the effect was caused by a modulation of the ring current location relative to the Earth due to the electric field. This electric field is required, as the magnetic field lines are considered frozen into the plasma in the magnetosphere. The closer location of the ring current to the Earth in turn increased the magnetic field at the surface.

  16. Electric-Field-Induced Superconductivity Detected by Magnetization Measurements of an Electric-Double-Layer Capacitor

    Kasahara, Yuichi; Nishijima, Takahiro; Sato, Tatsuya; Takeuchi, Yuki; Ye, Jianting; Yuan, Hongtao; Shimotani, Hidekazu; Iwasa, Yoshihiro

    2011-01-01

    We report evidence for superconductivity induced by the application of strong electric fields onto the surface of a band insulator, ZrNCl, provided by the observation of a shielding diamagnetic signal. We introduced an electric-double-layer capacitor configuration and in situ magnetization measureme

  17. Electric field modelling for point-plane gap

    The electric field distribution for point-plane gap is modelled both for stressed point and stressed plane electrodes. In simulations, the influence of the discharge chamber walls is taken into account. The size of an avalanche and the corresponding current pulse are calculated. The results are compared with those got other field distribution approximations. (author)

  18. Heavy ion injection for electric field generation in Tokamaks

    The injection of heavy ions such as Mg+ or Ca+ into a tokamak such that they are trapped in ''fat'' banana orbits is proposed as a technique for creation of a radial electric field. Such a field is of interest for improving the confinement of fuel ions relative to the confinement of alpha-particle ash

  19. Ultra-capacitor flexible films with tailored dielectric constants using electric field assisted assembly of nanoparticles.

    Batra, Saurabh; Cakmak, Miko

    2015-12-28

    In this study, the chaining and preferential alignment of barium titanate nanoparticles (100 nm) through the thickness direction of a polymer matrix in the presence of an electric field is shown. Application of an AC electric field in a well-dispersed solution leads to the formation of chains of nanoparticles in discrete rows oriented with their primary axis in the E-field direction due to dielectrophoresis. The change in the orientation of these chains was quantified through statistical analysis of SEM images and was found to be dependent on E-field, frequency and viscosity. When a DC field is applied a distinct layer consisting of dense particles was observed with micro-computed tomography. These studies show that the increase in DC voltage leads to increase in the thickness of the particle rich layer along with the packing density also increasing. Increasing the mutual interactions between particles due to the formation of particle chains in the "Z"-direction decreases the critical percolation concentration above which substantial enhancement of properties occurs. This manufacturing method therefore shows promise to lower the cost of the products for a range of applications including capacitors by either enhancing the dielectric properties for a given concentration or reduces the concentration of nanoparticles needed for a given property. PMID:26593234

  20. Ultra-capacitor flexible films with tailored dielectric constants using electric field assisted assembly of nanoparticles

    Batra, Saurabh; Cakmak, Miko

    2015-12-01

    In this study, the chaining and preferential alignment of barium titanate nanoparticles (100 nm) through the thickness direction of a polymer matrix in the presence of an electric field is shown. Application of an AC electric field in a well-dispersed solution leads to the formation of chains of nanoparticles in discrete rows oriented with their primary axis in the E-field direction due to dielectrophoresis. The change in the orientation of these chains was quantified through statistical analysis of SEM images and was found to be dependent on E-field, frequency and viscosity. When a DC field is applied a distinct layer consisting of dense particles was observed with micro-computed tomography. These studies show that the increase in DC voltage leads to increase in the thickness of the particle rich layer along with the packing density also increasing. Increasing the mutual interactions between particles due to the formation of particle chains in the ``Z''-direction decreases the critical percolation concentration above which substantial enhancement of properties occurs. This manufacturing method therefore shows promise to lower the cost of the products for a range of applications including capacitors by either enhancing the dielectric properties for a given concentration or reduces the concentration of nanoparticles needed for a given property.

  1. Numerical simulation of electromagnetic and flow fields of TiAI melt under electric field

    Zhang Yong; Ding Hongsheng; Jiang Sanyong; Chen Ruirun; Guo Jingjie

    2010-01-01

    This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAI melt under two electric fields. FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving. The melt in molds of same cross section area with different flakiness ratio (i.e. width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field. The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1. The melt is driven bipolarly from the center in each electric field. It is also found that the pulse electric field actuates the TiAI melt to flow stronger than what the sinusoidal electric field does.

  2. Confinement, fluctuations, and electric fields in the H-1 heliac

    Low density discharges produced by RF power of 50-100 kW at low magnetic field in the H-1 heliac are used to study transitions in confinement that are similar to those seen at high power in large devices. Probe diagnostics can be used to make detailed measurements of the profiles of plasma quantities, including the radial electric field. At transition, the density increases by a factor of about two, the density profile steepens, and the ion temperature increases. The transition is accompanied by a decrease in plasma turbulence and changes in the radial electric field. (author)

  3. Confinement, fluctuations, and electric fields in the H-1 HELIAC

    Low density discharges produced by RF power of 50-100 kW at low magnetic field in the H-1 heliac are used to study transitions in confinement that are similar to those seen at high power in large devices. Probe diagnostics can be used to make detailed measurements of the profiles of plasma quantities, including the radial electric field. At transition, the density increases by a factor of about two, the density profile steepens, and the ion temperature increases. The transition is accompanied by a decrease in plasma turbulence and changes in the radial electric field. (author)

  4. Time Evolution of Electric Fields in CDMS Detectors

    Leman, S W; Brink, P L; Cabrera, B; Chagani, H; Cherry, M; Cushman, P; Silva, E Do Couto E; Doughty, T; Figueroa-Feliciano, E; Mandic, V; McCarthy, K A; Mirabolfathi, N; Pyle, M; Reisetter, A; Resch, R; Sadoulet, B; Serfass, B; Sundqvist, K M; Tomada, A; Young, B A; Zhang, J

    2011-01-01

    The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3" diameter x 1" thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors, the later providing a $\\sim$1 V cm$^{-1}$ electric field in the detector bulk. Cumulative radiation exposure which creates $\\sim 200\\times 10^6$ electron-hole pairs is sufficient to produce a comparable reverse field in the detector thereby degrading the ionization channel performance. To study this, the existing CDMS detector Monte Carlo has been modified to allow for an event by event evolution of the bulk electric field, in three spatial dimensions. Our most resent results and interpretation are discussed.

  5. Design, fabrication and application of an SOI-based resonant electric field microsensor with coplanar comb-shaped electrodes

    This paper presents a highly sensitive resonant electric field microsensor based on silicon on insulator (SOI) technology. To improve the electric field coupling effect, the microsensor uses coplanar shutter electrodes and sense electrodes. To obtain higher conversion gain, both electrodes adopt novel comb-shaped structures. A finite element method (FEM) was used to simulate and optimize the structures of the comb-shaped electrodes. The sensitivity model of the microsensor was analyzed by the conversion gain of the vibration-amplitude-to-charge variation. The resolution of the microsensor is approximately 40 V m−1 with an uncertainty of 1% for the dc field, while the resolution is better than 10 V m−1 for the 50 Hz ac field. The microsensors were packaged and assembled to form an electric field probe to measure the atmospheric electric field. The test results showed that the probe precisely detected the occurrence of thunderstorms, and the plotted data agreed well with those of the conventional electric field mill. (paper)

  6. The electric field and global electrodynamics of the magnetosphere

    Stern, D. P.

    1979-01-01

    The conception of the electrodynamics of the quiet-time magnetosphere obtained during the last four years of magnetospheric study is presented. Current understandings of the open magnetosphere, convective plasma flows in the plasma sheet, the shielding of the inner magnetosphere from the convective magnetospheric electric field, the space charge produced when injected electrons drift towards dawn and injected ions drift towards dusk, the disruption of the flow of the Birkeland current by plasma instabilities and the shielding of the convective electric field by the dayside magnetopause are discussed. Attention is also given to changes of magnetic field line topology magnetic storms and substorms. Unresolved questions and new tools which may play a role in the further understanding of magnetospheric electrodynamics and the role of the magnetospheric electric field are presented.

  7. Kalman filtering techniques for focal plane electric field estimation

    Groff, Tyler D

    2013-01-01

    For a coronagraph to detect faint exoplanets, it will require focal plane wavefront control techniques to continue reaching smaller angular separations and higher contrast levels. These correction algorithms are iterative and the control methods need an estimate of the electric field at the science camera, which requires nearly all of the images taken for the correction. The best way to make such algorithms the least disruptive to science exposures is to reduce the number required to estimate the field. We demonstrate a Kalman filter estimator that uses prior knowledge to create the estimate of the electric field, dramatically reducing the number of exposures required to estimate the image plane electric field while stabilizing the suppression against poor signal-to-noise (SNR). In addition to a significant reduction in exposures, we discuss the relative merit of this algorithm to estimation schemes that do not incorporate prior state estimate history, particularly in regard to estimate error and covariance. ...

  8. The role of electric fields in the cometary environment

    Polarization electric fields in the cometary environment are shown to influence both the cometary plasma and the fine cometary dust. The role of the ambipolar electric field on the dynamics and thermodymamics of the cometary ionosphere is discussed. It is shown that this field decelerates and cools the plasma in the outer cometary ionosphere, and shock waves can develop in the plasma flow due to this deceleration. The consequences of electrostatic change of the cometary dust are considered. It is shown that while the consequences are minimal within the cometary ionosphere, they are substantial outside. The convectional electric field in the inflowing solar wind (both outside and inside the outer shock), as well as the Coulomb drag of this plasma on the charged dust, affect significantly the dynamics of the lower end of the dust mass spectrum. (author)

  9. Strong electric fields from positive lightning strokes in the stratosphere

    Holzworth, R. H.; McCarthy, M. P.; Thomas, J. N.; Chin, J.; Chinowsky, T. M.; Taylor, M. J.; Pinto, O.

    2005-02-01

    A balloon payload launched in Brazil has measured vector electric fields from lightning at least an order of magnitude larger than previously reported above 30 km in the stratosphere. During the flight hundreds of lightning events were recorded, including several positive cloud to ground lightning strokes. A two stroke flash, with small (15 kA peak current) and moderate (53 kA) positive strokes at a horizontal range of 34 km, produced field changes over 140 V/m at 34 km altitude. On-board optical lightning detection, recorded with GPS timing, coupled with ground based lightning location gives high time resolution for study of the electric field transient propagation. These measurements imply that lightning electric fields in the mesosphere over large thunderstorms may be much larger than previously measured.

  10. Electric field for tuning quantum entanglement in supported clusters

    We show that quantum entanglement, nowadays so widely observed and used in a multitude of systems, can be traced in the atomic spins of metal clusters supported on metal surfaces. Most importantly, we show that it can be voluntarily altered with external electric fields. We use a combination of ab initio and model Heisenberg–Dirac–Van Vleck quantum spin Hamiltonian calculations to show, with the example of a prototype system (Mn dimers on Ag(0 0 1) surface), that, in an inherently unentangled system an electric field can ‘switch on’ the entanglement and significantly change its critical temperature parameter. The physical mechanism allowing such rigorous control of entanglement by an electric field is the field-induced change in the internal magnetic coupling of the supported nanostructure. (paper)

  11. Premixed combustion under electric field in a constant volume chamber

    Cha, Min Suk

    2012-12-01

    The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity. © 2012 IEEE.

  12. Analyze and experiment on AC magnetic field's effect to fiber optic gyroscopes in compact stabilization control systems

    Zhang, Chao; Mao, Yao; Tian, Jing; Li, Zhijun

    2015-10-01

    Fiber optic gyroscopes (FOG) are getting more and more attention in areas such as stabilization control systems as they are all solid state and have a wide bandwidth. In stabilization systems that require wide bandwidth control, motors are usually used as actuating mechanism for active disturbance restrain. Voice coil motors (VCMs) are usually used in compact stabilization systems that require large torque and fast response. However, AC magnetic field, which can affect the output of FOG due to Faraday effect, will be generated during operation of VCMs. The frequency range affected by the AC magnetic field to the FOG's output is the same as VCMs drive signal frequency range, which is also exactly the stabilization system's working range. Therefore the effect of the AC magnetic field to FOGs must be evaluated to verify the feasibility of a stable system design that uses both FOGs and VCMs. In this article, the basic structure and operating principle of stabilization system is introduced. The influence of AC magnetic field to FOG is theoretically analyzed. The magnetic field generated by VCMs is numerically simulated based on the theory deduction of the magnetic field near energized wires. To verify the influence of the VCM generated magnetic field to the FOGs in practical designs, a simplified random fiber coil model is built for it's hard to accurately test the exact polarize axis's twisting rate in a fiber coil. The influence to the FOG's output of different random coil model is simulated and the result shows a same trend that the influence of the VCM's magnetic field to the FOG is reduced as the distance between the VCM and the FOG increasing. The influence of a VCM to a FOG with the same parameters is experimentally tested. In the Fourier transformed FOG data the same frequency point as the VCM drive signal frequency can be read. The result fit simulated result that as the distance increases, the influence decreases. The amplitude of the frequency point is just

  13. Time dependence of electrical bioimpedance on porcine liver and kidney under a 50 Hz ac current

    The purpose of this work is to study the changes of the bioimpedance from its 'in vivo' value to the values measured in a few hours after the excision from the body. The evolution of electrical impedance with time after surgical extraction has been studied on two porcine organs: the liver and the kidney. Both in vivo and ex vivo measurements of electrical impedance, measuring its real and imaginary components, have been performed. The in vivo measurements have been carried out with the animal anaesthetized. The ex vivo measurements have been made more than 2 h after the extraction of the organ. The latter experiment has been carried out at two different stabilized temperatures: at normal body temperature and at the standard preservation temperature for transplant surgery. The measurements show a correlation between the biological evolution and the electrical bioimpedance of the organs, which increases from its in vivo value immediately after excision, multiplying its value by 2 in a few hours

  14. Time dependence of electrical bioimpedance on porcine liver and kidney under a 50 Hz ac current

    Spottorno, J.; Multigner, M.; Rivero, G.; Álvarez, L.; de la Venta, J.; Santos, M.

    2008-03-01

    The purpose of this work is to study the changes of the bioimpedance from its 'in vivo' value to the values measured in a few hours after the excision from the body. The evolution of electrical impedance with time after surgical extraction has been studied on two porcine organs: the liver and the kidney. Both in vivo and ex vivo measurements of electrical impedance, measuring its real and imaginary components, have been performed. The in vivo measurements have been carried out with the animal anaesthetized. The ex vivo measurements have been made more than 2 h after the extraction of the organ. The latter experiment has been carried out at two different stabilized temperatures: at normal body temperature and at the standard preservation temperature for transplant surgery. The measurements show a correlation between the biological evolution and the electrical bioimpedance of the organs, which increases from its in vivo value immediately after excision, multiplying its value by 2 in a few hours.

  15. Manipulation of red blood cells with electric field

    Saboonchi, Hossain; Esmaeeli, Asghar

    2009-11-01

    Manipulation of bioparticles and macromolecules is the central task in many biological and biotechnological processes. The current methods for physical manipulation takes advantage of different forces such as acoustic, centrifugal, magnetic, electromagnetic, and electric forces, as well as using optical tweezers or filtration. Among all these methods, however, the electrical forces are particularly attractive because of their favorable scale up with the system size which makes them well-suited for miniaturization. Currently the electric field is used for transportation, poration, fusion, rotation, and separation of biological cells. The aim of the current research is to gain fundamental understanding of the effect of electric field on the human red blood cells (RBCs) using direct numerical simulation. A front tracking/finite difference technique is used to solve the fluid flow and electric field equations, where the fluid in the cell and the blood (plasma) is modeled as Newtonian and incompressible, and the interface separating the two is treated as an elastic membrane. The behavior of RBCs is investigated as a function of the controlling parameters of the problem such as the strength of the electric field.

  16. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  17. Water-methanol separation with carbon nanotubes and electric fields

    Winarto, Affa; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-07-01

    Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing diameter. In contrast, under an electric field, water molecules strongly prefer to occupy the CNTs over methanol molecules, resulting in a separation effect for water. More interestingly, the separation effect for water does not decrease with increasing CNT diameter. Formation of water structures in CNTs induced by an electric field has an important role in the separation of water from methanol.Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing

  18. Probing electric field control of magnetism using ferromagnetic resonance.

    Zhou, Ziyao; Trassin, Morgan; Gao, Ya; Gao, Yuan; Qiu, Diana; Ashraf, Khalid; Nan, Tianxiang; Yang, Xi; Bowden, S R; Pierce, D T; Stiles, M D; Unguris, J; Liu, Ming; Howe, Brandon M; Brown, Gail J; Salahuddin, S; Ramesh, R; Sun, Nian X

    2015-01-01

    Exchange coupled CoFe/BiFeO3 thin-film heterostructures show great promise for power-efficient electric field-induced 180° magnetization switching. However, the coupling mechanism and precise qualification of the exchange coupling in CoFe/BiFeO3 heterostructures have been elusive. Here we show direct evidence for electric field control of the magnetic state in exchange coupled CoFe/BiFeO3 through electric field-dependent ferromagnetic resonance spectroscopy and nanoscale spatially resolved magnetic imaging. Scanning electron microscopy with polarization analysis images reveal the coupling of the magnetization in the CoFe layer to the canted moment in the BiFeO3 layer. Electric field-dependent ferromagnetic resonance measurements quantify the exchange coupling strength and reveal that the CoFe magnetization is directly and reversibly modulated by the applied electric field through a ~180° switching of the canted moment in BiFeO3. This constitutes an important step towards robust repeatable and non-volatile voltage-induced 180° magnetization switching in thin-film multiferroic heterostructures and tunable RF/microwave devices. PMID:25631924

  19. Additional electric field in real trench MOS barrier Schottky diode

    Mamedov, R. K.; Aslanova, A. R.

    2016-04-01

    In real trench MOS barrier Schottky diode (TMBS diode) additional electric field (AEF) the whole is formed in the near contact region of the semiconductor and its propagation space is limited with the barrier metal and the metallic electrodes of MOS structures. Effective potential barrier height TMBS diode is formed via resulting electric field of superposition AEF and electric field of space charge region (SCR) semiconductor. The dependence of the resulting electric field intensity of the distance towards the inside the semiconductor is nonlinear and characterized by a peak at a certain distance from the interface. The thickness of the SCR in TMBS diode becomes equal to the trench depth. Force and energy parameters of the AEF, and thus resulting electric field in the SCR region, become dependent on the geometric design parameters TMBS diode. The forward I-V characteristic TMBS diode is described by the thermionic emission theory as in conventional flat Scottky diode, and in the reverse bias, current is virtually absent at initial voltage, appears abruptly at a certain critical voltage.

  20. Effect of Electric Field on Conductivity and Vickers Hardness of an A1-Li Alloy

    刘兵; 陈大融; 陈铮; 王永欣; 李晓玲

    2003-01-01

    Static electric fields were applied on an aluminium-lithium alloy during solution treatment.The conductivity and Vickers hardness of the quenched Al-Li alloy is changed with the effect of electric field.The Vickers hardness increases with the applied electric field for a certain solutionizing time but decreases with the time under an electric field.In the absence of the electric field,the Vickers hardness and the conductivity increase synchronously,while reversed after electric field treatment.Positive and negative electric fields had the similar effect.The change of the local electron density in alloy caused by electric field is presented to explain the effect.